My Big Fat Planet: Pick of the Pics

January 10th, 2013

By Amber Jenkins

View of Earth at Night    Earth at night, as seen by the Suomi National Polar-orbiting Partnership (NPP) satellite, a joint effort by NASA and the National Oceanic and Atmospheric Administration (NOAA). Courtesy of NASA Earth Observatory and NOAA National Geophysical Data Center.

This is a new image of our planet at night, as taken by a new NASA and National Oceanic and Atmospheric Administration (NOAA) satellite orbiting above us. Scientists recently unveiled this global composite image (and the one below), constructed using cloud-free nighttime images. They show the glow of natural and man-made phenomena across the planet in greater detail than ever seen before. City lights can tell us about how humans have spread across the globe.

View of Earth at Night

Many satellites are equipped to look at Earth during the day, when they can observe our planet fully illuminated by the sun. But with a new sensor onboard the NASA-NOAA Suomi National Polar-orbiting Partnership (NPP) satellite launched last year, scientists now can observe Earth’s atmosphere and surface during nighttime hours.

For more Earth at night images, see this article.

This post was written for “My Big Fat Planet,” a blog hosted by Amber Jenkins on NASA’s Global Climate Change site.

Slice of History: Viking Stereo Viewer

December 4th, 2012

By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at

Viking Stereo ViewerViking Stereo Viewer — Photograph Number 324-1954

This interactive computer-based stereo viewing system was used to analyze Mars topography images generated by the cameras on NASA’s Viking 1 Mars lander. Two 17-inch video monitors faced a scanning stereoscope mounted between them on a table. Left and right lander camera image data were sent to the left and right monitors. Panning controls on the stereoscope helped align one image with the other to create a stereo image, 640 by 512 pixels in size. A mouse was used for finely controlled rotation of the monitors. An article about the system described a prototype mouse, used before this photo was taken in 1976. “The track ball is a baseball-sized sphere protruding from the top of a retaining box and capable of being rotated freely and indefinitely about its center …”

The resulting images could be displayed on additional monitors and were used to create contour maps and other images that aided lander surface operations. The system was developed by Stanford University and NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

Short Puffs Keep Dawn Chugging Along

December 4th, 2012

By Marc Rayman
As NASA’s Dawn spacecraft makes its journey to its second target, the dwarf planet Ceres, Marc Rayman, Dawn’s chief engineer, shares a monthly update on the mission’s progress.

Artist's concept of the Dawn spacecraft at Ceres
Artist’s concept of NASA’s Dawn spacecraft at its next target, the protoplanet Ceres. Image credit: NASA/JPL-Caltech

Dear Dawndroids,

Dawn is continuing to gently and patiently change its orbit around the sun. In September, it left Vesta, a complex and fascinating world it had accompanied for 14 months, and now the bold explorer is traveling to the largest world in the main asteroid belt, dwarf planet Ceres.

Dawn has spent most of its time since leaving Earth powering its way through the solar system atop a column of blue-green xenon ions emitted by its advanced ion propulsion system. Mission controllers have made some changes to Dawn’s operating profile in order to conserve its supply of a conventional rocket propellant known as hydrazine. Firing it through the small jets of the reaction control system helps the ship rotate or maintain its orientation in the zero-gravity of spaceflight. The flight team had already taken some special steps to preserve this precious propellant, and now they have taken further measures. If you remain awake after the description of what the changes are, you can read about the motivation for such frugality.

Dawn’s typical week of interplanetary travel used to include ion thrusting for almost six and two-thirds days. Then it would stop and slowly pirouette to point its main antenna to Earth for about eight hours. That would allow it to send to the giant antennas of NASA’s Deep Space Network a full report on its health from the preceding week, including currents, voltages, temperatures, pressures, instructions it had executed, decisions it had made, and almost everything else save its wonderment at operating in the forbidding depths of space so fantastically far from its planet of origin. Engineers also used these communications sessions to radio updated commands to the craft before it turned once again to fire its ion thruster in the required direction.

Now operators have changed the pace of activities. Every turn consumes hydrazine, as the spacecraft expels a few puffs of propellant through some of its jets to start rotating and through opposing jets to stop. Instead of turning weekly, Dawn has been maintaining thrust for two weeks at a time, and beginning in January it will only turn to Earth once every four weeks. After more than five years of reliable performance, controllers have sufficient confidence in the ship to let it sail longer on its own. They have refined the number and frequency of measurements it records so that even with longer intervals of independence, the spacecraft can store the information engineers deem the most important to monitor.

Although contact is established through the main antenna less often, Dawn uses one of its three auxiliary antennas twice a week. Each of these smaller antennas produces a much broader signal so that even when one cannot be aimed directly at Earth, the Deep Space Network can detect its weak transmission. Only brief messages can be communicated this way, but they are sufficient to confirm that the distant ship remains healthy.

In addition to turning less often, Dawn now turns more slowly. Its standard used to be the same blinding pace at which the minute hand races around a clock (fasten your seat belt!). Engineers cut that in half two years ago but returned to the original value at the beginning of the Vesta approach phase. Now they have lowered it to one quarter of a minute hand’s rate. Dawn is patient, however. There’s no hurry, and the leisurely turns are much more hydrazine-efficient.

With these two changes, the robotic adventurer will arrive at Ceres in 2015 with about half of the 45.6-kilogram (101-pound) hydrazine supply it had when it rocketed away from Cape Canaveral on a lovely September dawn in 2007. Mission planners will be able to make excellent use of it as they guide the probe through its exploration of the giant of the main asteroid belt.

Any limited resource should be consumed responsibly, whether on a planet or on a spaceship. Hydrazine is not the only resource that Dawn’s controllers manage carefully, but let’s recall why this one has grown in importance recently.

› Continue reading Marc Rayman’s Dawn Journal

Slice of History: 1944 Map of JPL

November 1st, 2012

By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at

1944 Map of JPL1944 Map of JPL — Photograph Number HC 3-1294

On October 31, NASA’s Jet Propulsion Laboratory in Pasadena, Calif., celebrated its 76th anniversary. It began with a few individuals working on the Caltech campus and testing rocket motors in the Arroyo Seco. By the time this 1944 map of “The Project” was created, JPL was supported by Army Air Corps contracts and the site included more than 50 offices, labs and test facilities.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

Dawn Comes Closer to Go Farther

November 1st, 2012

By Marc Rayman
As NASA’s Dawn spacecraft makes its journey to its second target, the dwarf planet Ceres, Marc Rayman, Dawn’s chief engineer, shares a monthly update on the mission’s progress.

Artist's concept of the Dawn spacecraft at Ceres
Artist’s concept of NASA’s Dawn spacecraft at its next target, the protoplanet Ceres. Image credit: NASA/JPL-Caltech

Dear Indawnspensable Readers,

Dawn is making good progress on the second segment of its cosmic travels. Following more than a year of arduous but sensationally productive and exciting work revealing the fascinating character of the giant protoplanet Vesta, it is now patiently pursuing its next target, the mysterious dwarf planet Ceres, which resides farther from the sun. For the second (and final) time in its interplanetary journey, however, Dawn is about to turn around, going closer to the sun rather than farther away.

In August 2008, we saw in detail how it could be that even as the bold explorer travels outward in the solar system from Earth, past Mars, to Vesta, and then on to Ceres, it could occasionally appear to reverse course temporarily. We present here a shorter explanation for those readers who did not memorize the log explaining this perplexing behavior (you know who you are, and we do as well, but your secret remains safe under the terms of our reader privacy agreement).

Dawn orbits the sun, as do Vesta, Ceres, the other residents of the main asteroid belt, and the planets. All orbits, whether of these objects around the star at the center of our solar system, artificial satellites or the moon in orbit around Earth, or even Dawn when it was in orbit around Vesta, are ellipses (like flattened circles). Earth, for example, orbits the sun at an average distance of 150 million kilometers (93.0 million miles), which astronomers call one astronomical unit (AU). During its year-long revolution, however, our planet comes in to 0.98 AU from the sun and goes out to 1.02 AU. Earthlings manage quite nicely with these small variations. (Note that the seasons are not caused by the changes in distance but instead are a result of the tilt of Earth’s axis and thus the differing angles at which the warming rays of the sun arrive during the year. If the sun’s distance were all that mattered, the northern and southern hemispheres would have the same seasons.) So, orbiting bodies move smoothly between a minimum and a maximum range from their gravitational masters rather than remaining at a constant distance.

When Dawn was in orbit around Vesta, it accompanied that world on its regular journey around the sun. The table last month showing the probe’s progress over the five years of its deep space trek reminds us that Vesta’s path brings it as close to the sun as 2.15 AU and takes it out to 2.57 AU.

If Dawn had remained in orbit around Vesta, it would have continued to follow the same elliptical course as its host in the asteroid belt. The pair would have reached their maximum solar distance next month and then would have fallen back to 2.15 AU in September 2014. While visiting Vesta was extremely gratifying, this explorer’s ambitions are greater. It broke free of Vesta’s grip, its sights set on a new and distant alien destination.

Now the spacecraft is in its own independent orbit around the sun, and the persistent but gentle pressure of its advanced ion propulsion system gradually reshapes that orbit. At any moment, the orbit is an ellipse, and an instant later, it is a slightly different ellipse, courtesy of the thrust. As Dawn departed from Vesta only last month, its orbit is not yet dramatically different, but over the course of the coming years, the effect of the thrusting will be to change the orbit tremendously. To reach Ceres in 2015, the ship will enlarge and tip its elliptical course to match the motion of the dwarf planet around the sun. (Some of the parameters characterizing each object’s orbit are shown here.)

Although the ship’s orbit is growing, it will reach the current high point on Nov. 1. It will then be 2.57 AU from the sun and, just as in 2008 (albeit at a smaller distance), it will begin moving closer, even as it continues to thrust.

If Dawn stopped thrusting on Nov. 1, its elliptical orbit would carry it down to 2.19 AU from the sun in September 2014. That’s a higher orbit than Vesta’s but still well below what it needs to be for the rendezvous with Ceres. Astute readers have already anticipated that the plan is not to stop thrusting but to continue reworking the trajectory, just as a ceramicist gradually achieves a desired shape to create the envisioned artistic result. The ongoing thrusting will raise the low point of the orbit, so if the ship follows the flight plan, it will descend only to 2.45 AU in October 2013 before sailing outward again. By May 2014 it will have risen to the same solar altitude as it is now. All the thrusting in the interim will have altered its course so much, however, that it will not turn around then; rather, it will continue ascending to keep its 2015 appointment with Ceres.

› Continue reading Marc Rayman’s Dawn Journal

Slice of History: Is It a JPL Magic Trick?

October 9th, 2012

By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at

magnetic bearing
Is it a JPL magic trick? — Photograph 328-161Ac

In 1960 through 1961, several different experiments were conducted at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., in search of a frictionless bearing for use in space applications, gyroscopes and other machinery. There were cryogenic, gas and electrostatic types of bearings, and the photo above shows a magnetic bearing. It was suspended by counterbalancing the force of gravity and an electromagnet. A servo feedback system continually corrected the current flow through the electromagnet to keep it stable.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

Dawn’s Stellar Anniversary

September 27th, 2012

By Marc Rayman
As NASA’s Dawn spacecraft makes its journey to its second target, the dwarf planet Ceres, Marc Rayman, Dawn’s chief engineer, shares a monthly update on the mission’s progress.

Artist's concept of the Dawn spacecraft
Artist’s concept of NASA’s Dawn spacecraft. Image credit: NASA/JPL-Caltech

Dear Dawnniversaries,

On the fifth anniversary of the beginning of its ambitious interplanetary adventure, Dawn can look back with great satisfaction on its spectacular exploration of the giant protoplanet Vesta and forward with great eagerness to reaching dwarf planet Ceres. Today Earth’s robotic ambassador to the main asteroid belt is in quiet cruise, gradually reshaping its orbit around the sun so it can keep its appointment in 2015 with the mysterious alien world that lies ahead.

This anniversary resembles the first three more than the fourth. Its first years in space were devoted to spiraling away from the sun, ascending the solar system hill so it could gracefully slip into orbit around Vesta in time for its fourth anniversary. One year ago, Dawn was in the behemoth’s gravitational grip and preparing to map its surface in stereo and make other measurements. The subsequent year yielded stunning treasures as Dawn unveiled the wondrous secrets of a world that had only been glimpsed from afar for over two centuries. While at Vesta, it spiraled around the massive orb to position itself for the best possible perspectives. Its final spiral culminated in its departure from Vesta earlier this month. Now for its fifth anniversary, it is spiraling around the sun again, climbing beyond Vesta so that it can reach Ceres.

For those who would like to track the probe’s progress in the same terms used on previous (and, we boldly predict, subsequent) anniversaries, we present here the fifth annual summary, reusing the text from last year with updates where appropriate. Readers who wish to cogitate about the extraordinary nature of this deep-space expedition may find it helpful to compare this material with the logs from its first, second, third, and fourth anniversaries.

In its five years of interplanetary travels, the spacecraft has thrust for a total of 1060 days, or 58 percent of the time (and about 0.000000021 percent of the time since the Big Bang). While for most spacecraft, firing a thruster to change course is a special event, it is Dawn’s wont. All this thrusting has cost the craft only 267 kilograms (587 pounds) of its supply of xenon propellant, which was 425 kilograms (937 pounds) on September 27, 2007.

The fraction of time the ship has spent in powered flight is lower than last year (when it was 68 percent), because Dawn devoted relatively little of the past year to thrusting. Although it did change orbits extensively at Vesta, most of the time it was focused on exactly what it was designed and built to do: scrutinize the ancient world for clues about the dawn of the solar system.

The thrusting so far in the mission has achieved the equivalent of accelerating the probe by 7.14 kilometers per second (16,000 miles per hour). As previous logs have described (see here for one of the more extensive discussions), because of the principles of motion for orbital flight, whether around the sun or any other gravitating body, Dawn is not actually traveling this much faster than when it launched. But the effective change in speed remains a useful measure of the effect of any spacecraft’s propulsive work. Having accomplished slightly more than half of the thrust time planned for its entire mission, Dawn has already far exceeded the velocity change achieved by any other spacecraft under its own power. (For a comparison with probes that enter orbit around Mars, refer to this earlier log.)

Since launch, our readers who have remained on or near Earth have completed five revolutions around the sun, covering about 31.4 AU (4.70 billion kilometers or 2.92 billion miles). Orbiting farther from the sun, and thus moving at a more leisurely pace, Dawn has traveled 23.4 AU (3.50 billion kilometers or 2.18 billion miles). As it climbed away from the sun to match its orbit to that of Vesta, it continued to slow down to Vesta’s speed. Since Dawn’s launch, Vesta has traveled only 20.4 AU (3.05 billion kilometers or 1.90 billion miles) and the even more sedate Ceres has gone 18.9 AU (2.82 billion kilometers or 1.75 billion miles).

› Continue reading Marc Rayman’s Dawn Journal

Dawn’s Split from Asteroid Vesta - Mission Insider Explains

September 5th, 2012

By Marc Rayman
As NASA’s Dawn spacecraft makes its journey to its second target, the dwarf planet Ceres, Marc Rayman, Dawn’s chief engineer, shares a monthly update on the mission’s progress.

The dwarf planet Ceres as imaged by the Keck Observatory
NASA’s Dawn spacecraft departed the giant asteroid Vesta on Sept. 04, 2012 PDT to begin its journey to a second destination, the dwarf planet Ceres, which is seen in this image from the Keck Observatory on Mauna Kea, Hawaii. Image credit: NASA/JPL-Caltech, Keck Observatory, C. Dumas

Dear Marvestalous Readers,

An interplanetary spaceship left Earth in 2007. Propelling itself gently and patiently through the solar system with a blue-green beam of xenon ions, it gradually spiraled away from the sun. It sailed past Mars in 2009, its sights set on more distant and exotic destinations. In July 2011, it gracefully and elegantly entered orbit around the second most massive resident of the main asteroid belt, Vesta. It spent more than 13 months there scrutinizing the gigantic protoplanet with all of its sensors and maneuvering to different orbits to optimize its investigations, making myriad marvelous discoveries. After they traveled together around the sun for 685 million kilometers (426 million miles), the ship left orbit in September 2012 and is now headed for dwarf planet Ceres, the largest body between the sun and Neptune not yet visited by a spacecraft. No other probe has ever been capable of the amazing feats Dawn is performing, exploring two of the largest uncharted worlds in the inner solar system.

The population of the main asteroid belt numbers in the millions. Vesta is such a behemoth that Dawn has now single-handedly examined about eight percent of the mass of the entire belt. And by the time it finishes at the colossus Ceres, it will have investigated around 40 percent.

The expedition to Vesta has produced riches beyond everyone’s hopes. With 31,000 photos, 20 million visible and infrared spectra, and thousands of hours of neutron spectra, gamma ray spectra, and gravity measurements, Dawn has revealed to humankind a unique and fascinating member of the solar system family. More akin to Earth and the other terrestrial planets than to typical asteroids, Vesta is not just another chunk of rock. It displays complex geology and even has a dense iron-nickel core, a mantle, and a crust. Its heavily cratered northern hemisphere tells the story of more than 4.5 billion years of battering in the rough and tumble asteroid belt. Its southern hemisphere was wiped clean, resurfaced by an enormous impact at least two billion years ago and an even greater collision one billion years ago. These events excavated the 400-kilometer (250-mile) Veneneia and 500-kilometer (310-mile) Rheasilvia basins. The larger basin has a mountain at the center that towers more than twice the height of Mt. Everest; indeed, it soars higher than all but one of the mountains known in the solar system. The impacts were so forceful, they nearly destroyed Vesta. The fierce shock reverberated through the entire body and left as scars an extraordinary network of vast troughs near the equator, some hundreds of kilometers (miles) long and 15 kilometers (10 miles) wide.

The powerful impacts liberated tremendous amounts of material, flinging rocks far out into space, some of which eventually made it all the way to Earth. It is astonishing that more than one thousand meteorites found here came from Vesta. We have some meteorites from Mars, and we have some meteorites from the moon, but we have far, far more that originated in those impacts at Vesta, so distant in time and space. Vesta, Mars, and the moon are the only celestial bodies identified as the source of specific meteorites.

Scientists will spend years productively poring through Dawn’s fabulous findings and learning what secrets they hold about the dawn of the solar system, and many more people will continue to marvel at the spectacular sights of this alien world. But the emissary from Earth has completed its assignment there and moved on. It has spent most of its time since the previous log using its ion propulsion system to climb higher and higher above Vesta. This departure spiral is the mirror image of the approach spiral the robotic adventurer followed last year. The unique method of entering and leaving orbit is one of the many intriguing characteristics of a mission that uses ion propulsion. Without that advanced technology, this ambitious deep space adventure would be impossible.

As Dawn ascended, Vesta’s gravitational grip grew weaker and weaker. At some point along its spiral, the explorer was far enough and moving fast enough that Vesta could no longer hold it in orbit. As smoothly and tenderly as Vesta had taken Dawn in its embrace last year, it released its erstwhile companion, each to go its own way around the sun. The bond was severed at about 11:26 p.m. PDT yesterday, when they were 17,200 kilometers (10,700 miles) apart, separating at the remarkably leisurely speed of less than 33 meters per second (73 miles per hour). Many of our readers drove their cars that fast today (although we hope it was not in school zones).

Unlike missions that use conventional chemical propulsion, there was no sudden change on the spacecraft and no nail-biting on Earth. If you had been in space watching the action, you probably would have been hungry, cold, and hypoxic, but you would not have noticed anything unusual about the scene. Apart from a possible hint of self-satisfaction, Dawn would have looked just as it had for most of its interplanetary flight, a monument to humankind’s ingenuity and passionate drive to know the cosmos perched atop a blue-green pillar of xenon ions. If, instead, you had been in Dawn mission control watching the action, you would have been in the dark and all alone (until JPL Security arrived). There was no need to have radio contact with the reliable spaceship. It had already thrust for almost 2.9 years, or 58 percent of its time in space. Thrusting during escape was no different. No one was tense or anxious; rather, all the drama is in the spectacular results of the bold mission at Vesta and the promise of what is to come at Ceres. When Dawn entered orbit, your correspondent was dancing. When Dawn left orbit, he was sleeping serenely.

A month earlier, on August 8, with the craft more than 2,100 kilometers (1,300 miles) above the surface, patiently powering its way up through Vesta’s gravity field, one of the reaction wheels experienced an increase in internal friction. Reaction wheels are used to control a spacecraft’s orientation in the frictionless, zero-gravity conditions of spaceflight. By electrically changing a wheel’s spin rate, Dawn can rotate or stabilize itself. Protective software quickly detected the event and correctly responded by deactivating that wheel and the other two that were operating, switching to the small jets that are available for the same function, and reconfiguring other systems, including powering off the ion thrust and turning to point the main antenna to Earth.

A routine communications session the next day revealed to mission controllers what had occurred. They had planned long ago to turn the wheels off for the flight from Vesta to Ceres, so having them off a few weeks early was not a significant change. The team soon restored the spacecraft to normal operations and reformulated the departure plan, and on August 17 Dawn resumed its ascent. Because of the hiatus in thrusting, escape shifted from August 26 to September 4. The flexibility in the mission timeline provided by ion propulsion made this delay easy to accommodate.

In order to conserve the hydrazine propellant that the jets use, the bonus departure observations described before were curtailed, as they were not a high priority for the mission. Nevertheless, on August 25 and 26, at an altitude of around 6,000 kilometers (3,700 miles), the explorer did peer at Vesta once more with its camera and visible and infrared mapping spectrometer. The last time it had been this far away was July 21, 2011, during its descent to an unfamiliar destination. This time, 13 months later, the spacecraft turned back for a final gaze at the magnificent world it had unveiled during its remarkable time there, a world that prior to last year had appeared as little more than a tiny smudge among the stars for the two centuries it had been observed.

The delay in the departure schedule provided a convenient benefit. Vesta has seasons, just as Earth does, although they progress more slowly on that distant orb. August 20 was the equinox, when northern hemisphere spring began. Until then, the sun had been in Vesta’s southern hemisphere throughout Dawn’s residence there. While most of the northern hemisphere was revealed during the second high-altitude mapping orbit, the illumination of the landscape immediately around the north pole was even better for this last look. After radioing its parting shots to wistful mission controllers, the ship commenced its climb again.

And then, with an stunningly successful mission behind it, a newly explored world below it, and a mysterious dwarf planet ahead of it, the indomitable and indefatigable adventurer left Vesta forever.

Dawn is 18,500 kilometers (11,500 miles) from Vesta and 64 million kilometers (40 million miles) from Ceres. It is also 2.45 AU (367 million kilometers or 228 million miles) from Earth, or 910 times as far as the moon and 2.43 times as far as the sun today. Radio signals, traveling at the universal limit of the speed of light, take 41 minutes to make the round trip.

Dr. Marc D. Rayman
10:00 a.m. PDT September 5, 2012

› Read previous Dawn Journals by Marc Rayman

Landing Curiosity - NASA’s Next Mars Rover

August 5th, 2012

By Doug Ellison

Follow the excitement as NASA prepares to land, Curiosity, its most technically advanced rover ever on Mars. JPL Visualization Producer Doug Ellison shares live, behind-the-scenes action from the mission control room at NASA’s Jet Propulsion Laboratory in Pasadena, Calif..

Artist's concept of NASA's Mars rover Curiosity


Monday, August 6, 2012 1:13:26 AM

Welcome to Gale Crater. “Adam…you’re a genius!” I shout to Adam Steltzner. He pauses. Stops. Turns around. “I’m not a genius — I just work with a team of them.”

Thanks for the ride

Sunday, August 5, 2012 10:04:10 PM

The EDL Phase Lead, Adam Steltzner, has just thanked the cruise team for their 350-million-mile ride. “Curiosity is in fantastic shape, she’s here because you guys got her here. See you on Mars.”

Go Curiosity. And break out the peanuts.

Mars really has us now.

Sunday, August 5, 2012 10:03:56 PM

Ten thousand and sixty three. Sixty four. Sixty five. As quick as you can count it, our speed towards Mars is accelerating.

Mars is about half the diameter of Earth, but only about 10 percent as heavy as Earth. Even so — on its surface, gravity is about 38 percent that of Earth. In the next 28 minutes, we will gain another 3,000 miles per hour until Curiosity, heatshield ready, slams into the top of the Martian atmosphere.

40 billion to 1

Sunday, August 5, 2012 9:15:28 PM

A quiet approach to Mars as we watch a tiny plot of a graph. The X-band frequency that Curiosity is currently transmitting is a frequency of more than 8 Gigahertz — 8 billion cycles per second. As it rotates, that tiny little graph shows that frequency moving up and down, by about 0.2 Hz. One part in 40 billion. That little bounce up and down is the rotation of the spacecraft, two revolutions per minute. We have that accuracy because we’re bouncing a radio signal from the ground, up to spacecraft and back again. But that signal, after a final poll, will be going away.

Systems Go. Power Go. Thermal Go. Propulsion Go. Nav Go. Uplink Go. Avionics Go. Flight. Software Go. Fault Protection Go. Chief Engineer Go. EDL FLight System Go. Data Management Go. GDS Go. Telecom Go. ACS Go. EDL Activity Lead Go. ACE Go.

“You are clear to bring down the uplink.” So in just over 13 minutes time, Curiosity will no longer have that amazing signal to bounce back - and our little squiggly 1-in-40-billion line will be gone. We will just hear the spacecraft’s own transmitter from more than 150 million miles.

Curiosity is truly on her own.

A Final Check

Sunday, August 5, 2012 8:44:21 PM

This full poll of the flight team is a lengthy and exhaustive tour of the rover, the cruise stage and all the systems. My favorite call is from the chief engineer:

“We are green across the board”

That’s the word from Rob Manning — a veteran of four successful Mars landings. When Rob says things are green, you know you’re in good shape. If you were hoping to spend some time exploring the martian moon Deimos on your way to Gale Crater — please alight the rover now, we just crossed its orbit. Now there are 16,000 miles to go.

Calm before the Storm

Sunday, August 5, 2012 8:32:58 PM

Things got a little quiet in the control room. People heading out for some food before we get down to the business of landing on Mars. It takes huge team to watch over a spacecraft as complex, and activites and intricate as a Mars landing. As they get back to their consoles, they do a comm check to make sure they can all hear each other. Systems. Power. Thermal. Prop. Nav. Uplink. Flight Software. Fault Protection. EO Team Chief. GDS. Telecom. EDL Comm. ACS … the calls, and acronyms, go on and on. Now they are all back on console, the whole team is about to do a full system poll.

Can you hear me?

Sunday, August 5, 2012 7:59:37 PM

Between now and landing, Curiosity will use a total of eight antennas. The Deep Space Network is now listening to a medium-gain antenna transmitting on X-Band on the cruise stage. During entry, two low gain antennas on the back of the spacecraft continue that signal of “tones.” There are also low-gain antennas on the descent stage and the rover. However, Earth will have set at this time.

Meanwhile, a UHF antenna on the backshell, followed by another on the descent stage and finally one on the rover, will continue to transmit telemetry during landing. This data will be received by Mars Odyssey and Mars Reconnaissance Orbiter. Odyssey will relay it straight to Earth so we can track landing. Mars Reconnaissance Orbiter records everything it hears and sends it back a few hours later. Mars Express will also record just the pitch of this signal as a final backup.

The ground stations at the Canberra, Australia Deep Space Communications Complex will follow us the whole way — direct from the rover ’til Earth sets behind it — and from Odyssey and Mars Reconnaissance Orbiter as well. All the way to the ground, a complex system of systems will be trying to keep that tenuous link between Earth and Mars alive.


Sunday, August 5, 2012 5:58:00 PM

“Nominal” sounds like a very boring word, but in the world of spaceflight, nominal is engineer for “awesome.” Thanks to the Deep Space Network, we know just how nominal everything is. Deep Space Station 43, a 70-meter-diameter antenna in Tidbindilla, Austraila is currently receiving a steady stream of data at 2,000 bits per second that informs the engineers how all their subsystems are doing. Attitude control, thermal performance, power systems, avionics, propulsion, communication, the list is long. The flight team (meet them all here: just took a poll, and all subsystems are nominal. The MEDLI instrument is now powered up, and healthy. It’s talking to the flight computer, and the power system can see it drawing just 300 milliamps. It will record first-of-its-kind data on temperature, pressure and other readings through Curiosity’s heatshield during entry. This data will help us understand how the heatshield behaves and can help us make them better for the future. As MEDLI lives on the inside of the heatshield, it is thrown overboard when the heatshield is separated about six miles above the surface. Its data will be safely stored on the rover to be downlinked after landing.


Sunday, August 5, 2012 1:15:54 PM

When you’re a spacecraft it’s important to know which way you’re facing. If you know which way you’re facing, you know which way Earth is, so you can talk to home; which way the sun is, so you can get power on a solar array; and if you’re Curiosity, you know which way Mars is. There are two ways spacecraft typically orient themselves. One is called “three-axis stabilized,” which means the spacecraft uses thrusters and reaction wheels to keep itself pointed the right way. You may have heard about trouble with reaction wheels on the Mars Odyssey orbiter recently (it carries a spare just in case, and we’re now using it). Curiosity (as well as its older sisters Spirit and Opportunity, and Juno right now on its way to Jupiter) just spin their way through deep space. They point in one direction and spin, like a top. That spin stops the spacecraft wandering off and pointing somewhere else. Curiosity, all the way till after we wave goodbye to its cruise stage about 17 minutes before landing, spins at 2 rpm. During its 253-day cruise, Curiosity will have spun more than 720,000 times. It’s enough to give a rover a headache.

Three Degrees

Sunday, August 5, 2012 1:05:01 PM

I’ve arrived “on lab” (JPL-speak for “at the office”) to check up on our computer running Eyes on the Solar System ( that will be fed to NASA Television tonight. Looking up in the control room — I see we’ve just crossed 80,000 miles to go. Less than four- times the distance from Earth to our geostationary communication satellites. Mars is about 4,200 miles in diameter - so with a little high school trig, we can calculate that Mars would appear 3 degrees across to Curiosity. That’s six times larger than the size of the full moon from Earth. This time yesterday, Curiosity was only 170 mph slower than it is now. In the next 10 hours as it falls to Mars it gains another 5,000. As an astronaut onboard Apollo 13 said to mission control on their way home, “The world’s getting awful big in the window.”

The Runners Up

Friday, August 3, 2012 11:15:00 AM

Adam Steltzner (MSL EDL phase lead) is a great speaker and real highlight of today’s NASA Social event. A fantastic question from the audience asked what ideas for landing Curiosity were rejected.

The runner-up: airbags. There isn’t a fabric that we know of strong enough to handle the impact loads that a 899-kg rover would create. Good enough for the 180-kg of Spirit and Opportunity, but it just can’t get scaled up to something as big as Curiosity.

Third place: Put the rover on top of the rockets. The problem there is that the rover is so heavy, and the propellant tanks so large, that you would have a very tall vehicle prone to toppling over on touchdown.

It may look a little crazy — but the skycrane actually makes a lot of sense.

Speed Up, Slow Down

Thursday, August 2, 2012 5:12:47 PM

The art of flying between the planets is a balancing act of gravity, velocity, trajectory and timing. These variables come to a thrilling climax on Sunday evening as Curiosity reaches the Red Planet.

Launched into a trajectory around the sun in November 2011, Curiosity is currently in a solar orbit that just reaches the orbit of Mars. That trajectory means that, from the perspective of the sun, by noon Pacific time on August 1 Curiosity was travelling at 47,500 miles per hour. Yet Mars is travelling at more than 53,000 mph — some 5,500 mph faster than Curiosity. Left alone, Curiosity would soon begin a slow cruise back towards the orbit of Earth, while Mars would carry on along its own, faster trajectory.

But breathtaking accuracy by the navigation team guiding Curiosity means that Mars will be at the right place Sunday to pick up Curiosity. The planet’s gravity will speed up the spacecraft by 13,000 mph (as viewed from the sun) until their speeds match and Curiosity is safely on the surface. On the freeway of interplanetary navigation, Curiosity is the bug, and Mars is the windshield. To get ready for a martian year of exploration, you’ve got to take a big hit.

Welcome to the Landing Blog

Thursday, August 2, 2012 5:12:16 PM

Welcome to the Curiosity landing blog. I’m Doug Ellison, a visualization producer here at JPL. Our group is responsible for many of the graphics you will see that show how Curiosity has made its way to Mars, and what it will do when it gets there.

The landing animation was a nine-month-long project of obsessing over details of every piece of the spacecraft and its adventure. We’ve launched a special version of Eyes on the Solar System at that lets you ride with Curiosity all the way to the surface. We’ve become so familiar with the spacecraft and what it does that we even surprise the mission team themselves sometimes!

On landing night, I’ll be in our mission control (the “Dark Room”) keeping you up to date with some of the goings-on as Curiosity approaches Mars. Until then I’ll post a few little factoids about Curiosity, its trip to Mars, and its epic landing at Gale Crater.

Slice of History: Free Fall Capsule Drop Test

August 2nd, 2012

By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at

Free Fall Capsule Drop Test
Free Fall Capsule Drop Test — Photograph Number 354-595

In 1961, a drop capsule was developed at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., by Section 354, Engineering Research. It was an experimental chamber to study how liquids behave in free-fall (zero gravity). The prototype capsule was dropped from a helicopter hovering at 800 feet, but the capsule was found to be too unstable for these tests. In September 1962, a trial drop was done from the Bailey bridge that connected JPL to the east parking lot. Testing was then moved to a bridge crossing Glen Canyon near Page, Arizona. The dam was under construction at the time and provided a 672-foot-fall with a soft dirt impact area.

The 204 pound shell contained a high-impact sequence camera designed for this experiment, a stopwatch, a liquid sample and a release mechanism. Three external motion picture cameras with different focal lengths looked down on the capsule as it fell. Although the capsule fell for about 10 seconds without rolling, pitching or yawing, there were problems with the internal release mechanism. It appears the experiment was discontinued after two attempts.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

Dawn Sets Its Sights on Ceres

July 30th, 2012

By Marc Rayman

As NASA’s Dawn spacecraft investigates its first target, the giant asteroid Vesta, Marc Rayman, Dawn’s chief engineer, shares a monthly update on the mission’s progress.

near-true color image of the remarkable snowman feature on asteroid Vesta's surface
Three impact craters of different sizes, arranged in the shape of a snowman, make up one of the most striking features on Vesta, as seen in this view from NASA’s Dawn mission. In this view the three “snowballs” are upside down, so that the shadows make the features easily recognizable. North is to the lower right in the image, which has a resolution of 230 feet (70 meters) per pixel. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Dear Dawnpartures,

Dawn has completed the final intensive phase of its extraordinary exploration of Vesta, and it has now begun its gradual departure. Propelled by its uniquely efficient ion propulsion system, the probe is spiraling ever higher, reversing the winding path it followed into orbit last year.

In the previous log (which gained prominence last month by making it into the list of the top 78 logs ever written on this ambitious interplanetary adventure), we saw the plan for mapping Vesta from an altitude of 680 kilometers (420 miles). In this second high-altitude mapping orbit (HAMO2), the spacecraft circled the alien world beneath it every 12.3 hours. On the half of each orbit that it was on the day side, it photographed the dramatic scenery. As it passed over the night side, it beamed the precious pictures to the distant planet where its human controllers (and many of our readers) reside. Tirelessly repeating this strategy while Vesta rotated allowed Dawn’s camera to observe the entirety of the illuminated land every five days.

The robot carried out its complex itinerary flawlessly, completely mapping the surface six times. Four of the maps were made not by pointing the camera straight down at the rocky, battered ground but rather at an angle. Combining the different perspectives of each map, scientists have a rich set of stereo images, allowing a full three dimensional view of the terrain that bears the scars of more than 4.5 billion years in the main asteroid belt between Mars and Jupiter.

Dawn also mapped Vesta six times during the first high-altitude mapping orbit (HAMO1) in September and October 2011. The reason for mapping it again is that Vesta has seasons, and they progress more slowly than on Earth. Now it is almost northern hemisphere spring, so sunlight is finally reaching the high latitudes, which were under an impenetrable cloak of darkness throughout most of Dawn’s residence here.

For most of the two centuries this mysterious orb had been studied from Earth, it was perceived as little more than a small fuzzy blob in the night sky. With the extensive imaging from HAMO1 and HAMO2, as well as from the low-altitude mapping orbit (LAMO, earthlings now know virtually all of the protoplanet’s landscape in exquisite detail.

Among the prizes for the outstanding performance in HAMO2 are more than 4,700 pictures. In addition to the comprehensive mapping, Dawn collected nearly nine million spectra with its visible and infrared mapping spectrometer (VIR) to help scientists determine more about the nature of the minerals. This phenomenal yield is well over twice that of HAMO1, illustrating the great benefit of dedicating valuable observation time in HAMO2 to VIR before the mapping.

Dawn’s measurements of the peaks and valleys, twists and turns of Vesta’s gravity field, from which scientists can map the distribution of material in the interior of the behemoth, were at their best in LAMO. That low altitude also was where the gamma ray and neutron detector (GRaND) obtained its finest data, revealing the atomic constituents of the surface and subsurface. Indeed, the motivation for undertaking the challenging descent to LAMO was for those investigations, although the bonus pictures and spectra greatly enhanced the reward. Even in HAMO2, however, gravity and GRaND studies continued, adding to an already fabulous bounty.

Mission controllers have continued to keep the distant spacecraft very busy, making the most of its limited time at Vesta. Pausing neither to rest nor to marvel or delight in its own spectacular accomplishments, when the robot finished radioing the last of its HAMO2 data to Earth, it promptly devoted its attention to the next task: ion thrusting.

Missions that use conventional propulsion coast almost all of the time, but long-time readers know that Dawn has spent most of its nearly five years in deep space thrusting with its advanced ion propulsion system, the exotic and impressive technology it inherited from NASA’s Deep Space 1. Without ion propulsion, the exploration already accomplished would have been unaffordable for NASA’s Discovery Program and the unique exploit to orbit both Vesta and dwarf planet Ceres would have been quite impossible. Ion propulsion not only enables the spacecraft to orbit residents of the main asteroid belt, something no other probe has attempted, but it also allows the interplanetary spaceship to maneuver extensively while at each destination, thus tailoring the orbits for the different investigations.

On July 25 at 9:45 a.m. PDT, as it has well over 500 times before, the sophisticated craft began emitting a beam of high-velocity xenon ions. In powered flight once again, it is now raising its orbital altitude. On August 26, the ship will be too far and traveling too fast for Vesta’s gravity to maintain its hold. Dawn will slip back into orbit around the sun with its sights set on Ceres.

Although HAMO2 is complete, the spacecraft will suspend thrusting four times to direct its instruments at Vesta during the departure phase, much as it did in the approach phase. The approach pictures aided in navigation and provided tantalizing views of the quarry we had been seeking for so long. This time, however, we will see a familiar world receding rather than an unfamiliar one approaching. But as the sun creeps north, advancing by about three quarters of a degree of latitude per week, the changing illumination around the north pole will continue to expose new features.

› Continue reading Marc Rayman’s Dawn Journal

Slice of History: Remote Controlled Manipulators

July 10th, 2012

By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at

Remote Controlled Manipulators
Remote Controlled Manipulators — Photograph Number 381-4778B

The NASA Jet Propulsion Laboratory’s 1971 Annual Report featured this photo of a remote controlled system for handling solid propellants. A 1965 Space Programs Summary report indicated that the equipment had been ordered and would be installed in building 197 within a few months. This equipment made it possible to safely mix and load high energy solid propellants into small motors. Building 197 is still known as the Solid Propellant Engineering Laboratory.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

A Different Slant:

July 9th, 2012

By Duane Roth

Cassini Has a Special View of Saturn These Days - How Did It Get There?

For the past 18 months, NASA’s Cassini spacecraft has been orbiting Saturn in practically the same plane as the one that slices through the planet’s equator. Beginning with the Titan flyby on May 22, navigators started to tilt Cassini’s orbit in order to obtain a different view of the Saturnian system. The measure of the spacecraft orbit’s tilt relative to Saturn’s equator is referred to as its inclination. The recent Titan flyby raised Cassini’s inclination to nearly 16 degrees. Seven more Titan flybys will ultimately raise Cassini’s inclination to nearly 62 degrees by April 2013. On Earth, an orbit with a 62-degree inclination would pass as far north as Alaska and, at its southernmost point, skirt the latitude containing the tip of the Antarctic Peninsula.

These graphics show the orbits NASA's Cassini spacecraft has made and will make around the Saturn system from September 2010 to April 2013.These graphics show the orbits NASA’s Cassini spacecraft has made and will make around the Saturn system from September 2010 to April 2013. As shown in gray, Cassini orbited within the plane of Saturn’s equator during the first 18 months of its current mission phase, known as the Solstice mission. Then, starting in May 2012, Cassini used the gravity of Saturn’s largest moon, Titan, to tilt its orbit as shown in the magenta loops, reaching a maximum tilt of about 62 degrees in April, 2013. Titan’s orbit is shown in red. The orbits of Saturn’s inner moons are shown in black. Image credit: NASA/JPL-Caltech

You may wonder why this change has been planned and how this feat is achieved. The “why” is to allow scientists to observe Saturn and the rings from different geometries in order to obtain a more comprehensive three-dimensional understanding of the Saturnian system. For instance, because Saturn’s rings lie within Saturn’s equatorial plane, they appear as a thin line when viewed by Cassini in a near-zero-degree orbit inclination. From higher inclinations, however, Cassini can view the broad expanse of the rings, making out details within individual ringlets and helping to unlock the secrets of ring origin and formation. Some of those images have already started to come in.

At higher inclinations, Cassini can also obtain excellent views of Saturn’s poles, and measure Saturn’s atmosphere at higher latitudes via occultation observations, where radio signals, sunlight or starlight received after passing through the atmosphere help to determine its composition and density.

The “how” is by using the gravity of Titan — Saturn’s largest moon by far — to change the spacecraft’s trajectory. Like the rings and Cassini’s previous orbit, Titan revolves around Saturn within a plane very close to Saturn’s equatorial plane. As Cassini flies past Titan, Titan’s gravity bends the spacecraft’s path by pulling it towards the moon’s center — similar to a ball bearing rolling on a smooth horizontal surface past a magnet. Near Titan, the motion is confined to a plane containing the spacecraft’s path and Titan’s center of mass. If this “local” plane coincides with Cassini’s orbital plane about Saturn, the trajectory’s inclination will remain unchanged. However, if this plane differs from Cassini’s orbital plane about Saturn, then the bending from Titan’s gravity will have a component out of Cassini’s orbital plane with Saturn, and this will change the tilt of the spacecraft’s orbit. Repeated Titan flybys will raise Cassini’s orbit inclination to nearly 62 degrees by April of next year and then lower it back to the Saturn equatorial plane in March 2015.

This view, from the imaging camera of NASA's Cassini spacecraft, shows the outer A ring and the F ring of SaturnNASA’s Cassini spacecraft has recently resumed the kind of orbits that allow for spectacular views of Saturn’s rings. This view, from Cassini’s imaging camera, shows the outer A ring and the F ring. The wide gap in the image is the Encke gap, where you see not only the embedded moon Pan but also several kinky, dusty ringlets. A wavy pattern on the inner edge of the Encke gap downstream from Pan and a spiral pattern moving inwards from that edge show Pan’s gravitational influence. The narrow gap close to the outer edge is the Keeler gap. Image credit: NASA/JPL-Caltech/SSI

Gravity assists are key to Cassini’s ever-changing orbital geometries. Onboard propellant alone would quickly become depleted attempting to accomplish these same changes. A gravity assist can be characterized by the amount of “delta-v,” or change in the velocity vector, it imparts to a spacecraft. Delta-v may of course also be imparted to the spacecraft via rocket engines and, either way, alters the spacecraft’s orbit. The eight Titan gravity assists responsible for raising Cassini’s inclination to 62 degrees will provide a delta-v of 15,000 mph (6.6 kilometers per second). For comparison, Cassini’s rocket engines had only enough propellant after initially achieving orbit around Saturn to deliver about 2,700 mph (1.2 kilometers per second) of delta-v. That’s 15,000 mph of capability spread over 11 months via gravity assists versus a modest 2,700 mph of capability spread over more than 13 years via rocket engines! Because delta-v is a vector, it may change both the speed and direction of Cassini at a point along its orbit, so the speed of Cassini is not changing by 15,000 mph, but mostly all of the directional changes sum to 15,000 mph. To give these values some context, Cassini’s speed typically varies between as low as 2,500 mph (1.1 kilometers per second) and as high as 79,000 mph (35 kilometers per second) relative to Saturn between apokrone and perikrone, the farthest and closest points from Saturn along its orbit. Gravity assists from the initial prime mission Titan flyby in 2004 to the final Solstice Mission Titan flyby in 2017 will provide nearly 200,000 mph (90 kilometers per second) of delta-v, leveraging the onboard propellant by a ratio of 75 to 1. The bulk of the Saturn tour trajectory is shaped by gravity assists, while the role of onboard propellant is to fine-tune the trajectory.

At the end of year 2015, Cassini will again begin climbing out of Saturn’s equatorial plane in preparation for its grand finale. After reaching an inclination of nearly 64 degrees, a Titan gravity assist in April 2017 will change Cassini’s perikrone so that Cassini will pass through the narrow 2,000-mile (3,000-kilometer) gap between Saturn’s atmosphere and innermost ring. Twenty-two spectacular orbits later, one final distant Titan gravity assist will alter Cassini’s course for a fiery entry into Saturn’s atmosphere to end the mission.

Shedding Light on the Scarred Face of Asteroid Vesta

July 5th, 2012

By Marc Rayman

As NASA’s Dawn spacecraft investigates its first target, the giant asteroid Vesta, Marc Rayman, Dawn’s chief engineer, shares a monthly update on the mission’s progress.

Image of the giant asteroid Vesta taken by NASA's Dawn spacecraft
This image, from NASA’s Dawn spacecraft, shows rock material that has moved across the surface and flowed into a low area in the ridged floor of the Rheasilvia basin on Vesta. The image shows how impacts and their aftermath constantly reshape the landscape. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/PSI

Dear Upside Dawn Readers,

Dawn is now seeing Vesta in a new light. Once again the probe is diligently mapping the ancient protoplanet it has been orbiting for nearly a year. Circling the alien world about twice a day, the ardent adventurer is observing the signatures of Vesta’s tortured history, including the scars accumulated during more than 4.5 billion years in the main asteroid belt between Mars and Jupiter.

Having successfully completed its orbital raising maneuvers to ascend to its second high-altitude mapping orbit (HAMO2), Dawn looks down from about 680 kilometers (420 miles). This is the same height from which it mapped Vesta at the end of September and October 2011. The lifeless rocky landscape has not changed since then, but its appearance to the spacecraft’s sensors has. The first high-altitude mapping orbit (HAMO1) was conducted shortly after southern hemisphere summer began on Vesta, so the sun was well south of the equator. That left the high northern latitudes in the deep darkness of winter night. With its slower progression around the sun than Earth, seasons on Vesta last correspondingly longer. Thanks to Dawn’s capability to linger in orbit, rather than simply conduct a brief reconnaissance as it speeds by on its way to its next destination, the probe now can examine the surface with different lighting.

Much of the terrain that was hidden from the sun, and thus the camera, during HAMO1 is now illuminated. Even the scenery that was visible then is lit from a different angle now, so new observations will reveal many new details. In addition to the seasonal northward shift in the position of the sun, Dawn’s orbit is oriented differently in HAMO2, as described last month, so that makes the opportunity for new insights and discoveries even greater.

The strategy for mapping Vesta is the same in HAMO2 now as it was in HAMO1. Dawn’s orbital path takes it nearly over the north pole. (As we saw last month, the orbit does not go exactly over the poles but rather reaches to 86 degrees latitude. That slight difference is not important for this discussion.) During the ship’s southward passage over the sunlit side, the camera and the visible and infrared mapping spectrometer (VIR) acquire their precious data. After passing (almost) above the south pole, Dawn sails north over the night side. Instead of pointing its sensors at the deep black of the ground below, the probe aims its main antenna to the extremely distant Earth and radios its findings to the exquisitely sensitive receivers of the Deep Space Network. The pattern repeats as the indefatigable spacecraft completes loop after loop after loop around the gigantic asteroid every 12.3 hours.

As Dawn revolves, Vesta rotates on its axis beneath it, turning once every 5.3 hours. Just as in HAMO1, mission planners artfully choreographed this celestial pas de deux so that over the course of 10 orbits, lasting just over five days, the camera would be able to view nearly all of the lit surface. A set of 10 orbits is known to Dawn team members (and to you, loyal readers) as a mapping cycle.

Until a few months ago, HAMO2 was planned to be four cycles. Thanks to the determination in April that Dawn could extend its residence at Vesta and still meet its 2015 appointment with dwarf planet Ceres, HAMO2 has been increased to six mapping cycles (plus even a little more, as we shall see below), promising a yet greater scientific return.

In cycle 1, which began on June 23, the camera was pointed at the surface directly underneath the spacecraft. The same view will be obtained in cycle 6. In cycles 2 through 5, images are acquired at other angles, providing different perspectives on the complex and dramatic landscape. Scientists combine the pictures to formulate topographical maps, revealing Vesta’s full three-dimensional character from precipitous cliffs and towering peaks of enormous mountains to gently rolling plains and areas with mysterious ridges and grooves to vast troughs and craters punched deep into the crust. Knowing the elevations of the myriad features and the angles of slopes is essential to understanding the geological processes and forces that shaped this exotic mini-planet. In addition to the exceptional scientific value, the stereo imagery provides realistic, exciting views for anyone who wants to visualize this faraway world. If you have not traveled there yourself, be sure to visit the Image of the Day regularly and the video gallery occasionally to see what you and the rest of humankind had been missing during the two centuries of Vesta’s appearance being only that of a faint, tiny blob in the night sky.

› Continue reading Marc Rayman’s Dawn Journal

Dawn Goes Over ‘n’ Out

June 4th, 2012

By Marc Rayman

As NASA’s Dawn spacecraft investigates its first target, the giant asteroid Vesta, Marc Rayman, Dawn’s chief engineer, shares a monthly update on the mission’s progress.

Images of the giant asteroid Vesta taken by NASA's Dawn spacecraft in 2011 and 2012
On May 3, 2011, the mapping camera on NASA’s Dawn spacecraft captured its first image (left) of the giant asteroid Vesta. Only 5 pixels across, the image didn’t provide any new information about the asteroid, but it was important for navigation purposes and provided an exciting first look at Dawn’s eventual target. About five months later, Dawn snapped the much more detailed image on the right from only 700 kilometers (435 miles) from the surface of Vesta and has since provided unparalleled views of the mysterious world. Image credit: NASA/JPL-Caltech

Dear Readers of all Dawnominations,

Far from Earth, on the opposite side of the sun, deep in the asteroid belt, Dawn is gradually spiraling around the giant protoplanet Vesta. Under the gentle pressure of its uniquely efficient ion propulsion system, the explorer is scaling the gravitational mountain from its low-altitude mapping orbit (LAMO) to its second high-altitude mapping orbit (HAMO2).

Dawn spent nearly five months in LAMO, circling the rocky world at an average altitude of 210 kilometers (130 miles) as it acquired a fabulous bounty of pictures; visible, infrared, neutron, and gamma ray spectra; and measurements of the gravity field. As we saw last month, the probe was far more productive in each investigation than the ambitious team members had expected or had ever dared hope it would be. With that outstanding success behind it, it is looking ahead and up to its work in HAMO2, about 680 kilometers (420 miles) high.

Dawn is the first spacecraft to explore Vesta, the second most massive resident of the main asteroid belt between Mars and Jupiter. Indeed, this is the only craft ever to orbit a body in the asteroid belt. No other missions are currently on the books to visit this remote, exotic world, which is now appreciated to be more closely related to the terrestrial planets (including Earth) than to typical asteroids. And now Dawn is receding from it. On May 1, it began the slow ascent to its next observation orbit. It may well be decades before another robotic ambassador from Earth comes as close to Vesta as this bold traveler has.

Humankind’s first exploration of Vesta has been exceptionally rewarding. A simple measure of that can be seen with just two photographs. More than two centuries after its discovery, this giant asteroid was first glimpsed by the approaching spaceship from Earth on May 3, 2011. From a distance of 1.2 million kilometers (750 thousand miles), or more than three times the separation between Earth and the moon, Dawn’s mapping camera perceived Vesta as only five pixels across. Each pixel spanned more than 110 kilometers (70 miles), revealing nothing new compared to what astronomers’ most powerful telescopes had shown (but the image was of importance for navigation purposes). Nevertheless, at the time, it was tremendously exciting to obtain the first views of a distant, unfamiliar shore after a voyage of more than 2.6 billion kilometers (1.6 billion miles) on the interplanetary ocean. Sighting our first celestial port of call more than three and a half years after this cosmic adventure began was thrilling indeed. But now, with more than 25 thousand spectacular photos in hand from much smaller distances, it is even more gratifying to acknowledge that first picture as one of the worst ever taken of Vesta. The Image of the Day from one year later
was acquired in October 2011 from 1,700 times closer; and most of the images have been obtained from LAMO, about 5,700 times nearer than that first one. Dawn has rapidly transformed Vesta from a mere fleck among the stars into a fascinating, complex and splendidly detailed world.

Keeping the remote vessel on the planned spiraling course from one mapping orbit to another presents the crew with a set of formidable challenges, but this team has accomplished the maneuvers to successively reach survey orbit, the first high-altitude mapping orbit (HAMO1) and LAMO. The current orbital transfer is complex and demanding, but it is proceeding very well. Controllers update the flight profile every few days to ensure the probe stays close to the carefully designed trajectory to HAMO2. To gain a sense of the progress, go here for your correspondent’s atypically succinct weekly summaries of the spiral status.

› Continue reading Marc Rayman’s Dawn Journal

Slice of History: Something is Missing …

June 4th, 2012

By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at

A large pond and smaller building 264 at JPL
Something is Missing … — Photograph Number JB-16114B

To anyone who came to NASA’s Jet Propulsion Laboratory in Pasadena, Calif., after 1975, this photo may seem odd – building 264 has only two stories, and there is a large pond running down the middle of the mall.

In September 1970, construction began on building 264, the Systems Development Laboratory, a support facility for the Space Flight Operations Facility in building 230. A 7.5 foot tunnel connected the two buildings, lined with racks to support the cables and wiring that joined them. It was constructed as a two story building with a foundation capable of supporting six additional floors, although JPL had to wait several years for additional funding to be approved. The building was finally completed late in 1975, providing mission support for the Viking and Voyager missions, computer space, and three floors of office space.

The pond was nearly 300 feet long, stretching from the mall fountain to a parking area at the east end of building 183. It was built in 1967 and removed by about 1989, but the fountain remains.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.

Slice of History: Scanning Electron Microscope

May 10th, 2012

By Julie Cooper

Each month in “Slice of History” we feature a historical photo from the JPL Archives. See more historical photos and explore the JPL Archives at

Scanning Electron Microscope
Scanning Electron Microscope — Photograph Number 354-1043B

In late 1967, this Stereoscan Mark VI scanning electron microscope (SEM) was delivered to NASA’s Jet Propulsion Laboratory by the Cambridge Instrument Company. They were in high demand at the time, and JPL had to wait nearly a year between placing the order and delivery. It was used by the Electronic Parts Engineering Section Failure Analysis Laboratory to examine microcircuits for defects. Other possible uses were for the study of metals and other materials, and to examine spores for the Capsule Sterilization Program. It used an electron beam to scan the specimen rather than visible light, at a magnification of 20X to 50,000X. The camera on the front right side could be used to record the images.

This post was written for “Historical Photo of the Month,” a blog by Julie Cooper of JPL’s Library and Archives Group.