GLAST Update for 23 June 2008
What is GLAST doing now?
After relatively simple, but important, software modifications were transmitted up to the spacecraft, some of the previously tested maneuvers were repeated to verify the software installation was successful. The onboard use of the GPS orbit position information is now also spot-on.
GLAST is ready for instrument turn-on, which will start early tomorrow morning! First, power will be fed to the instruments, then their onboard computers will be booted up and configured. GBM will start turning on first, followed by the LAT a few hours later. Much of the next couple of days will be spent turning on and checking the many sensor subsystems on the LAT. We're very excited to start waking up the instruments after all these years of planning and testing.
Thoughts before waking up the instruments
On the eve of instrument turn-on, here are some thoughts of some of the members of the instrument teams. First, from Dr. Chip Meegan, who is the GBM Principal Investigator at Marshall Space Flight Center:
The GBM team is eagerly anticipating the beginning of science operations on GLAST. Our many years of hard work will soon be rewarded with the first real data from space. Right now our only task is monitoring the temperatures of our detectors. The good news is that these are very close to predictions. Over the next week we will gradually power up GBM, verify that everything is working properly, and adjust the detector gains and other software parameters.
We have learned a lot about gamma-ray bursts (GRBs) in recent years. We now know that that these events have incredible power, releasing as much energy in a few seconds as the sun will over its entire 10 billion year lifetime. Although we have some idea of how this happens in general, the details remain mysterious. Working together, the LAT and GBM will observe gamma radiation over an unprecedented range of photon energies, shedding new light on how GRBs work. I am particularly interested in
what we will learn about a mystery that we got a glimpse of with the Compton Gamma Ray Observatory. It appears that at least some bursts generate high energy photons (in the LAT range) after the lower energy photons (in the GBM range) have ceased. This is difficult to understand theoretically, and GLAST will be able to study this in detail, perhaps telling us something important about how the photons are produced.
As Steve has often said, the most interesting things will be the new mysteries that GLAST discovers. GRBs have surprised us many times over the years, and I don't expect them to stop now.
The following is by Prof. Robert Johnson, from U.C. Santa Cruz. The most complex part of the LAT by far is the Tracker (TKR) subsystem, and you can bet that Robert, as the TKR Subystem Manager, will be particularly interested in the progress of LAT turn on during the next few days. Robert is also currently the co-coordinator of the LAT science group preparing to search for signals of dark matter and possible new physics. I asked him what he most hopes will be learned with GLAST.
For me, the most exciting signal that GLAST could see would be gamma rays produced by dark matter. Given the preponderance of gravitational evidence for dark matter, together with its complete lack so far of any other direct signature, its composition is one of the greatest mysteries in astrophysics. It is amazing that despite our tremendous progress in physics and astrophysics we still do not know what makes up most of the matter in the universe. Current theories bring ideas in fundamental physics together with the latest in cosmology and astrophysics to try to explain this mystery. Since I began my career in experimental particle physics, it would be wonderful to use GLAST to make further connections between those fields and to begin to resolve the great dark matter enigma.
Progress turning on the instruments, plus more news from around the international GLAST team. Please check back during the next couple of days.