NASA Blog: LCROSS: First Step and First Glance: Day 2
20 June 2009 – Paul D. Tompkins
Another late night for Shift A…we are staffing from around 11:30 AM to about 1 AM the next morning, so I don’t get to writing until the wee hours. Today was another great day at NASA Ames as our team settled into our mission plan and continued through a number of “firsts”. Each operations shift is trained in two roles – one with a “planning” emphasis, and the other with an “execution” emphasis. Shift B has taken the “planning” side of things for the first few days. However, last night, in addition to planning, Shift B continued Activation & Checkout where Shift A left off. They performed a full checkout of our attitude control system, among other things. For the first few days, Shift A (my shift) gets the fun, with Activation & Checkout (yesterday), Trajectory Correction Maneuver 1 (TCM 1) and “Quicklook” today, and TCM 2 tomorrow. Shift B takes over the fun for the remaining two days, with TCM 3, Star Field Calibration, and the capstone event for the week – Lunar Swingby.
Today, we had two major events. TCM 1 is our most important “burn” for the first week. It is intended to remove any targeting errors introduced by the Centaur upper stage as it injected us into our Trans-Lunar Orbit. Our navigation team determined our Centaur delivery was quite accurate, but it’s actually a very lucky day that a launch vehicle places a spacecraft precisely on its target orbit. It’s not a knock on the launch vehicle industry, it’s just that they have a really difficult job. Hey, it’s rocket science after all! Our Mission & Maneuver Design team designed TCM 1 and arrived at a burn plan with 8.06 m/s “delta-v”, the resulting change in velocity, for a total commanded on-time of 9 minutes 40 seconds. Coupled with the burn was a “pitch flip” to re-orient our primary omni-directional antenna towards the Earth.
The burn went off better than in any simulation. We had our command sequences loaded 30 minutes early, and the LCROSS spacecraft operated far more smoothly than our simulator ever did. Our power system is working tremendously – our solar array was providing positive charge to the batteries while pointed 60 degrees off the sun. Attitude control was smooth, and our 22 Newton thrusters performed as we had hoped. Our mission-critical maneuver, one that we had spent so many weeks worrying about over the past few years, was over before we knew it, and our trajectory is now far better matched to the target. Only time (and our Navigation team) will tell precisely how it went. All initial signs are positive!
Our second goal was to perform “Quicklook”, an extension of Activation & Checkout, but for the science payload. The LCROSS payload has a special place in the hearts of team members, since it was developed here at NASA Ames. The scientists and payload engineers poured countless hours into instrument development, integration and testing. All of the spacecraft team watched them do it, and know what effort they went through.
Quicklook is a fairly simple functional test of the science instruments, the Data Handling Unit and of general science data flow from the spacecraft to Earth. An onboard commmand sequence powers the DHU, which in turn powers the instruments, and commands each instrument to operate for a few minutes and to return data. To simplify the test operationally, we make no attempt to point the payload to the Earth or moon yet, so to anyone but a scientist on our team, the results aren’t very exciting. But to the Science Team, the data speaks volumes. Quicklook might be a simple and mundane test, but the results are critically important to LCROSS. Our mission is all about the science payload in the end, and problems here have a direct negative effect on our bottom line.
The Flight Team kicked off the command sequence and watched as our payload successfully powered up, and began sending data. One by one, the instruments delivered. The Science team displayed the data in real time, and we watched the bit streams turn into images (very black, since we’re looking into dark space) and spectra. Quicklook was finished in 23 minutes, and later this evening, the Science and Payload teams went home looking very satisfied! Another milestone achieved, and a good result for the more interesting payload tests in the next few days.
Other than the planned events, our team has been busy characterizing how the spacecraft REALLY behaves. It’s one thing to know the design, and how it SHOULD operate. But models are only so good, but the actual physics of a spacecraft in its environment define how it will act. It’s amusing because in several cases, “problems” we detected we later realized are intended or at least understood behaviors of the design, initially misinterpreted. We’ve been working with LCROSS for years, and only now, as it recedes away from Earth, are we truly learning its personality.
As a closing thought, I wanted to relate a common thread of thought amongst our team. For those of us who have been in the same room as the LCROSS spacecraft so many days/weeks/months, it is a strange thought that we just shot that familiar piece of hardware off the Earth and sent it on its way to the moon, and despite that enormous distance, we can still “talk” to it like we did in the clean room. You’d think years of preparation would dull us to the idea, but the Flight Team is struck by how similarly the flight is to those days in tests!
As always, thank you for the great comments, questions and well-wishes. More tomorrow! GO LCROSS! Now, time for sleep.
