Archive for September, 2008

Big Wheeling for Extreme Science - the Mars Science Laboratory

Monday, September 29th, 2008
by Robert Hogg
Robotics Engineer

Mars Science Laboratory is a mission to create and send to Mars the largest, most capable and most exciting rover that has been sent to another planet to date. It will be a remote robotic scientist that will help us investigate our most Earth-like neighbor in the solar system. It is literally a mobile laboratory — the size of a car, with a wide array of science instruments that will help us determine whether Mars has the capability to support life, both in the past and in the present.

Most of my work at JPL has been in the area of research robotics, small projects with very focused goals, such as the Urban Robot project, the Spiderbot, and many others. These robots were created using a small team of engineers who each covered a wide area of responsibility such as mechanical, electrical, and different areas of computer science for perception and navigation.

Here is a great animation showing everything that Mars Science Laboratory will accomplish, as well as all the different mechanisms and systems that will have to work remotely a hundred million miles away on Mars.

At times, to get one of these robots working right we would “hack” together a solution, and get it implemented in a very short amount of time! By throwing our energy and ideas into each project, we could push the cutting edge of different technologies and robotic capability that could then be used by future projects and researchers.

In contrast I’m now working on the motor control system of the Mars Science Laboratory mission, which as opposed to research is a “flight project” (it’s going to fly!). This is quite a different experience than the research area - the mission is kind of like taking the goal or purpose of the robot, breaking it down into a million pieces, and putting every piece under a microscope to make sure everything will work absolutely perfectly. Instead of 10 or fewer engineers each working on the different subsystems of the robot, we have hundreds of engineers and scientists who are planning, designing, developing, manufacturing, testing and in general creating a very complicated remote-sensing system.

Latest Mechanical Integration Progress

Sending a robot of any kind to another planet is a completely different story than running any such thing on Earth. For one thing, the robot must operate within very extreme temperatures and handle harsh exposure to the sun’s rays. Future robots may have to deal with steep or challenging terrain, or even a lack of a solid surface such as on Titan, Saturn’s largest moon. And throughout all this, the robot has to work perfectly and stay in communication with Earth. There is no control-alt-delete button to handle software crashes, and no technician around who can run out to push the big red reset button. In other words, if you’re going to run a robot on another planet, it has to land unharmed, work the first time, and run correctly every time you command it to do something, so that you’re guaranteed to get back the vital science data you’re after.

From the Edge

Tuesday, September 23rd, 2008
Ed Stone
by Ed Stone
Voyager Project Scientist

Winds of charged particles race outwards from the sun at 300,000 miles per hour. They are so faint that, here on the outer edge of the solar system, they would be undetectable if it were not for the very sensitive instruments carried by spacecraft.

From this distant, dark void, the sun is 100 times farther away than it is from Earth. Even so, our star is a million times brighter than Sirius, the brightest star seen from Earth. All around is a near-perfect vacuum, with only the most capable of instruments able to detect an ambient magnetic field that is 200,000 times weaker than the field back on Earth. To top off the loneliness factor, nothing from Earth has ever journeyed this far from home.

This remote zone is the domain now for Voyager 1 and 2.After 31 years of exploration, the twin spacecraft are the elder statesmen of space exploration, robotic envoys in the most distant reaches of our solar system. Voyager 1 is now 107 times farther from the sun than Earth is; Voyager 2 is 87 times farther. It takes about 15 hours for a signal leaving Earth to reach Voyager 1. (By contrast, it takes a little more than 20 minutes for a signal to go to Mars, even when the red planet is farthest from Earth.)

This artist’s rendering depicts NASAs Voyager 2 spacecraft as it studies the outer limits of the heliosphere - a magnetic ‘bubble’ around the solar system that is created by the solar wind.

The twin spacecraft do not rest on the laurels of their discoveries at Jupiter, Saturn, Uranus and Neptune - the planets they flew by between 1977 and 1989. In fact, their findings at our solar system’s edge are changing scientists’ theories about what happens “way out there” and how interstellar space affects our solar system.

The Voyagers have shown that the heliosphere - the sun’s protective bubble surrounding our solar system — is not smooth and symmetric, as was originally thought. The robotic team discovered that this bubble is being pushed in and deformed by the pressure from the interstellar magnetic field outside our solar system. Another surprise came when the spacecraft passed an important milestone near the edge of the solar system, called the termination shock. The energy released from the sudden slowing of the sun’s supersonic wind had an unexpected outcome - it was absorbed not by the wind itself, but by ionized atoms that had come from outside our solar system. And inevitably, as theories are shattered in the wind, more questions arise. There are cosmic rays we know come from this distant region, for example, but their origin is yet to be found and explained.

After all this time, Voyager’s discoveries continue to do what they have always done - take us to new places we have never been, and shed light on the how our solar system interacts and interconnects with the surrounding regions of the Milky Way.

Both Voyagers have enough power to run until 2025. Voyager 1 will probably cross into interstellar space by about 2015. At that moment, Voyager 1 will become Earth’s first interstellar spacecraft, leaving the sun behind as it enters the interstellar wind produced by the supernova explosions of other stars.

Until their final transmissions — hopefully many years in the future — the Voyagers still have a long way to go and lots to tell us.

Progress With Phoenix

Tuesday, September 16th, 2008
Deborah Bass
by Deborah Bass

Since Phoenix landed in the northern hemisphere of Mars, the spacecraft has discovered:

1. Water ice near the surface of Mars! And it is really close to the surface, as the orbiting Odyssey spacecraft predicted, and Phoenix confirmed. This demonstrates science in action: data, hypothesis, confirmation of hypothesis.

2. The pH of Martian arctic soil is basic (or alkaline), rather than acidic. On Earth, soil pH is important because most food plants prefer an acidic or neutral soil to grow. Bacteria usually thrive in acidic soils as well. So what we found on Mars is not necessarily the best news for the search for life. One thing I think astrobiologists would agree upon, however, is that life is very adaptable and can exist in many extreme environments!

lumps of ice
These lumps of ice, in a trench nicknamed
“Dodo-Goldilocks,” sublimated, a process similar to
evaporation, over the course of four days. › Image and caption

3. Unlike the landing sites of the Spirit and Opportunity rovers near the planet’s equator, there are no soils with sulfur compounds, or sulfates, in this part of Mars. Spirit and Opportunity found that the soils at their landing sites were cemented together with sulfur compounds. Sulfates do not act as cementing chemicals where Phoenix landed in the Martian arctic.

4. The soil grains Phoenix found are a mixture of angular and rounded particles, with a myriad of colors from rust to white to black. They show degrees of weathering and different chemical compositions.

5. There are high level clouds and ground fogs every night, and the general weather patterns are repeatable.

6. A chemical called perchlorate appears to be prevalent in the soil. On Earth, perchlorate forms in arid areas where there is very little rainfall. The team is still working to understand how perchlorate affects whether life could have existed in this region on Mars.

What does all of this mean? Well for starters, Mars has a diverse geology and geochemistry, much like Earth. Making generalizations about Mars planetwide is probably not the right approach, because of the planet’s diversity. What does it all mean for the bigger picture? Ah, that’s where the difficult science comes in. This takes time. Many members of the science team expect to have their findings ready by December, to coincide with a big science conference in San Francisco. So stay tuned!

Getting Ready for Mars in 110 Degree Heat

Monday, September 8th, 2008
by Ravi Prakash

Who ever thought that being in the desert in the middle of summer would be so much fun?!

I’m working on a mission called the Mars Science Laboratory, the next rover that NASA is going to send to Mars. Its mission is to help us find out whether or not Mars might have offered a favorable environment for life at one point in time (read more about the mission).

I’m part of the group designing the mission’s entry, descent, and landing phase, also known as the “7 minutes of terror.” This is a really exciting part of the mission because we’re trying to slow the spacecraft down from over 12,500 mph (about 5 times as fast as a speeding bullet) to a screeching halt in about 7 minutes! To do this, so many things have to go right in such a small amount of time. Once the spacecraft enters the Martian atmosphere, and because it’s going so fast, the spacecraft gets hotter than the surface of the sun. Then we deploy a parachute supersonically (faster than the speed of sound), fire retro-rockets at a very precise altitude, and gently lower the rover to the surface of Mars on a bridle (see the animation here). No one ever said rocket science was easy!

Artist concept of Mars Science Lab’s parachute descending to Martian surface.

Since so many things need to happen perfectly, we test things here on Earth before we launch the spacecraft to Mars. One of my responsibilities includes field testing the radar, which will tell the spacecraft how far off the ground it is and how fast it is going during its descent. If the radar doesn’t work properly, the spacecraft could fire its rockets at the wrong time and crash on the surface of Mars. That would be a very, very bad day.

For the test, the radar was suspended between two towers.

To make sure the radar will work on Mars, a group of us went out to the desert two weeks ago to test it out. The weeks leading up to the test were pretty frantic, with numerous hurdles along the way as we were trying to get the system working in the lab. After we got it working, we took it out to the desert where we attached our radar to a cable, which was attached to a pulley, and all of this in turn was suspended between two towers about 400 feet tall. The other end of the cable was attached to a truck. When the truck drove forward, the radar was lowered at about the speed that it will be descending on Mars just prior to landing.

The testing was so successful that we finished a day early, and were able to leave the really hot desert. We ended up with great data that will help us improve our radar so that it will work flawlessly on Mars. The success of this test made the hard work and desert heat all worth it. But when it was all said and done, we were all pretty glad to go back home, rest and then come back to work to start the cycle over for our next two sets of radar tests–on a helicopter and an F-18 jet!