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. No one ever said rocket science was easy!
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.
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!
Almost everyone has had the frustrating experience of getting lost. To avoid this problem, the savvy traveler carries a map. Similarly, astronomers need maps of the sky to know where to look, allowing us to make the best use of precious time on large telescopes. A map of the entire sky also helps scientists find the most rare and unusual types of objects, such as the nearest star to our sun and the most luminous galaxies in the universe. Our team (lead by our principal investigator, Dr. Ned Wright of UCLA) is building a new space telescope called the Wide-field Infrared Survey Explorer that will make a map of the entire sky at four infrared wavelengths. Infrared is a type of electromagnetic radiation with a wavelength about ten or more times longer than that of visible light; humans perceive it as heat.
Why do we want to map the sky in the infrared? Three reasons: First, since infrared is heat, we can use it to search for the faint heat generated by some of the coldest objects in the universe, such as dusty planetary debris discs around other stars, asteroids and ultra-cold brown dwarfs, which straddle the boundary between planets and stars. Second, we can use it to look for very distant (and therefore very old) objects, such as galaxies that formed only a billion years after the Big Bang. Since light is redshifted by the expansion of the universe, the most distant quasars and galaxies will have their visible light shifted into infrared wavelengths. And finally, infrared light has the remarkable property of passing through dust. Just as firefighters use infrared goggles to find people through the smoke in burning buildings, astronomers can use infrared to peer through dense, dusty clouds to see things like newborn stars, or the dust-enshrouded cores of galaxies.
So how does one go about building an infrared space telescope? And why does it need to be in space in the first place? Since infrared is heat, you can imagine that trying to observe the faint heat signatures of distant astronomical sources from our nice warm Earth would be very difficult. A colleague of mine compares ground-based infrared astronomy to observing in visible light during the middle of the day, using a telescope made out of fluorescent light bulbs! Putting your infrared telescope in the deep freeze of space, well away from the warmth of Earth, improves its sensitivity by orders of magnitude over a much larger ground-based infrared telescope.
On the Wide-field Infrared Survey Explorer project, our team is in the middle of one of the most exciting phases of building a spacecraft -- we're assembling and testing the payload. Right now, the major pieces of the observatory have been designed and manufactured, and we're in the process of integrating all these pieces together. The payload is elegantly simple. It has only one moving part -- a small scan mirror designed to "freeze-frame" the sky for each approximately 10 second exposure as the spacecraft slowly scans. After six months, we will have imaged the entire sky. The telescope is flying the latest generation of megapixel infrared detector arrays, along with an off-axis telescope that gives us the wide field of view that we need to cover the whole sky so quickly. In the next few months, we'll be setting the focus on our telescope, characterizing our detector arrays, and verifying the thermal performance of our cryostat. The observatory's cryostat is essentially a giant thermos containing the cryogenic solid hydrogen that we use to keep our telescope and detectors at their operating temperatures near absolute zero.
We are also in the midst of making detailed plans for verifying that the spacecraft is working properly once we launch. This is called the "in-orbit checkout" phase. For this mission, checkout is fast -- only 30 days! The checkout commences right after our November 2009 launch, when we wake the spacecraft up and begin switching on its various subsystems: Power generation and distribution, communications, attitude control and momentum management, and the main computer system. We'll also power on the payload electronics and detectors. Next, we will begin the calibration observations that we need to start the survey, such as verifying the telescope's image quality and the way our detector arrays respond to light. Once these steps are completed, we'll be ready to extend our gaze across the universe using the observatory's infrared eyes.
The great thing about the mission's all-sky dataset is that it will be accessible to everyone in the entire world via a Web interface. So you will literally be able to access some of the coldest, most distant and dustiest parts of the universe from the comfort of your couch. Stay tuned to explore the universe with us!