February 25, 2002
"It was a very long day here in snowy Russia," reports JPL engineer Jennifer Owens. It is 28 days before Grace, the Gravity Recovery and Climate Experiment, is scheduled to launch from Plesetsk in Northern Russia on a mission to make precise measurements of Earth's gravity field.
Owens is one of a small group of engineers from JPL and Astrium, the German company that built the two Grace satellites, who have come to Russia to oversee the final preparations before launch. Their job is to test and re-test everything and be sure all is ready for launch. The days are long and the stakes are high.
Owens has been reporting back regularly to her colleagues at JPL on Grace's preparations. For a behind-the-scenes look at some of what goes on before a launch, here are some brief excerpts of her communiques.
Launch - 27 days
We have four heartbeats!
Both spacecraft were moved into the turnover trolleys (the frames on which the satellites are mounted while they are being worked on) today. All four ultra-stable oscillators -- "heartbeats"-- are powered via external power. They will warm up through the night.
Flight model 1 (one of the twin Grace satellites) was powered up near the end of the day today, and thus far, all systems look good. It looks like the trip through the cold wasn't so cold after all.
Tonight on the movie list, South Park episodes and "Crouching Tiger, Hidden Dragon."
Launch - 25 days
We've been Busy as Beavers the Past Few Days
Everything works! In the spirit of the Olympic games, we have decided that we are peaking at the right time!
Today the Astrium team ran a test on flight model 2 (one of the two Grace satellites) --everything worked well.
We also ran an instrument test on flight model 1 (the other Grace satellite). As with yesterday, the test was a complete success. I am very happy to report that both spacecraft are working great!
We recorded one hour of K-band ranging data on each of the four microwave assemblies.The team is pretty excited to have made it through this hurdle with such success. The global positioning system is working very well (the antenna location is wonderful, and this definitely shows in the performance we are seeing), the star cameras all checked out well.
Today also marked the start of another exciting event-fueling! Fueling began on both satellites, and the propulsion guys seemed very happy with the results thus far. They performed a thruster test, and Charley (Dunn) held his hand in front of one of the orbit control thrusters--he says, "you know, it's really amazing that this will push us through space..." Deep down we all have a little space geek in us, and I think the feeling of the day was unanimous - thrusters are cool.
The mechanical team was very busy today performing close-out work on flight model 2. There was some harness work done such as cable tie installation, cable tieback, etc. Also, the solar panel attachment holes were stuffed with aluminized Mylar. This was a neat operation to watch, as the delicate work was done with tweezers and a rather large wad of Mylar.
Also, we have installed a windsock. . . . It was quite a show to watch the installation, as the Russian team helping us had to climb over some pretty high snow banks to get to the mounting location. Luckily, the weather was great today (about 0 degrees C), so the snow was well packed instead of fresh (and easy to sink into).
Some final notes...
Viktor (Kerzhanovich) has perfected the locking/sealing of doors. He has installed security locks on our office door.
Along these same lines, our seal/lock was so good, we locked Bert (Turney) out!! Oops! We're a little punchy late in the afternoon, and somehow, we got on the bus, and were driving away when we realized we very effectively sealed Bert out of the room with his warm clothing in it. Sorry Bert!
Grace is set to launch on March 16. Unlike most satellites that make observations with independent scientific instruments onboard, the Grace satellites are themselves the primary instrument. They are equipped with global positioning system receivers that provide very precise information about the satellite's locations and linked by a K-band microwave beam that can measure the distance between the two satellites to less a micron (the thickness of a red blood cell).
As the Grace satellites orbit Earth, one in front of the other, variations in Earth's gravitation field will cause the distance between the two satellites to change. By measuring these changes very precisely, Grace will be able to map Earth's gravitational field 1,000 times more accurately than it has been mapped before and show how it changes over time. The results will be important for many disciplines, including oceanography, hydrology, geology and climate studies.