GLAST Update 23 June

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.

Coming up…

Progress turning on the instruments, plus more news from around the international GLAST team.  Please check back during the next couple of days.

GLAST Update 22 June

GLAST Update 22 June 2008

What is GLAST doing now?

We’re almost two weeks into the mission now, and things continue to go well, thanks to coordinated efforts across the team.  Over the weekend, the spacecraft onboard attitude control software was further tested, with more challenging pointing sequences, autonomous repoints (once the instruments are activated and configured, they can request the spacecraft to change its orientation to keep a gamma-ray burst location detected onboard within the LAT field of view.  This is similar to what is done on the Swift satellite), and rehearsals for Targets of Opportunity (TOOs — quick-response repointing of the observatory via ground command — which we expect to do for GLAST only under extraordinary conditions, but we want to be ready!).  With such complex maneuvers, there have been a few interesting hiccups, all of which have been quickly understood and addressed.  Everything continues to function in a very stable manner, and it has been great fun watching the observatory move from baby steps to sophisticated, graceful motions.

Operating a spacecraft

Jack Leibee, one of my colleagues at Goddard, is the Mission Manager for GLAST (he is also the Systems Manager).  I asked him to write a few thoughts from his perspective about what it’s like to operate a satellite like GLAST:

Getting ready to operate a spacecraft, once it is in orbit, is a very demanding task.  For the last year and a half, we have been testing between the GLAST Operations Center and the spacecraft to verify that all commanding procedures are correct, as well as confirming that we have all the tools necessary (e.g. plotting and displaying observatory data) to monitor the performance of GLAST.  We conducted well over 300 hours of this type of testing, while GLAST was on the ground, executing around 400 command procedures.  We also conducted 10 simulations, where we had all the folks who are going to support the mission execute the activation command procedures with a GLAST simulator.  In some of the pre-launch tests, the Simulation Director inserted anomalies (e.g. a component fails) to test the operations team ability to respond: figure out what happened, why it happened, and how to recover back to normal operations.

During launch and ascent to orbit, we watched the spacecraft telemetry in the Mission Operations Center.  We also saw the spacecraft react to separation from the rocket by pointing to the Sun and deploying the solar arrays (needed to provided power to the spacecraft.)  Over the next 10 days we have been turning on spacecraft components and checking out the spacecraft (e.g. Slewing (moving) the spacecraft to look at different points in the sky) to verify it meets requirements.  This is all in preparation for the instrument turn on of the LAT and GBM in just a couple of days.

It has been an exciting and rewarding time for all of us as we see the results of everyone’s hard work and dedication.

Coming up…

In addition to regular status updates, you’ll be able to read about the GLAST Education and Public Outreach activities, as well as reports from other scientists working on GLAST from around the world about their hopes and expectations as the instruments are powered on and checked out.  Please check back regularly.

GLAST Update 19 June 2008

Update 19 June 2008

Observatory News 

Yesterday was another great day for GLAST.   After several days of successful maneuvering tests (see previous blog entry), it was time to activate the antenna that will very soon be used for science data transmission.  A gimbal points the antenna to one of several satellites in the Tracking and Data Relay Satellite System (TDRSS).  Engineers working in the Mission Operations Center had previously checked out the gimbal, solving a few minor glitches along the way.  The transmitter was activated yesterday, and the performance of the communication link was even better than expected!  After some initial tests, the link was used to dump data from the onboard solid state recorder (SSR), which temporarily stores the data pending transmission to the ground.  The data transmission contacts typically last about 15 minutes, and 5-10 contacts per day are planned during routine operations. 

The observatory is now smoothly executing the standard sky survey observing pattern while performing test data transmissions — which means GLAST is almost ready to start turning on its instruments next week, after just a few more preparatory steps.  Then the work to calibrate and tune the instruments for the on-orbit environment can begin, a process that will take many weeks of hard — but rewarding — work.  Stay tuned!

News from Italy

The following is from Prof. Ronaldo Bellazzini, who is the INFN Italian team coordinator:

There has been great interest in Italy in these weeks for the GLAST launch. GLAST has been on the national or local media media almost every day!
  Our sponsor agencies (INFN, ASI, and INAF) are programming a further set of events related to the forthcoming milestones (LAT activitation, first light results, first skymap…).  Please visit this link for information on the launch-related public outreach activities in Italy.

The launch was the culmination of many years of hard work by many people coming from different scientific and technical cultures.  In Italy, as elsewhere, GLAST has been the result of a strong partnership between the particle physics and high-energy astrophysics communities.  We have united our efforts to share important science goals and technical expertise.  All members of the INFN team (from the Trieste, Udine, Padova, Pisa, Perugia, Roma2 and Bari INFN sections) are anxious for LAT activation and for first-light results from the instrument we have proudly contributed to building and testing.

We are sure that GLAST is starting its journey toward extraordinary discoveries that will help change our understanding of the Universe.

News from the LAT Instrument Science Operations Center (ISOC)

The following is from Dr. Eduardo do Couto e Silva, a Deputy Manager of the ISOC at SLAC and a LAT Team member:

We are just a few days away from turning on the LAT!  The team will be ready and waiting for the data, working in close coordination with our colleagues at the Mission Operations Center at Goddard Space Flight Center.  We are organizing about 100 of our collaborators around the world, who will be involved in LAT operations and who will take shifts at the Stanford Linear Accelerator Center (SLAC) in California, so that the LAT and its data can be monitored continuously.   Data will flow through the ISOC, for processing, and made available to the rest of the LAT team.  The LAT Collaboration distributed worldwide will work with those at SLAC to inspect the quality of the data and to ensure we have a calibrated telescope whose performance is optmized for the best scientific return.  This is a huge effort, and we are ready for the challenges ahead.  We can’t wait to see the gamma-ray sky through GLAST “eyes” and to share with the world what we find in the months and years ahead.

Coming up…

In future posts, we will have contributions from other GLAST team members from around the world.  Please check back every few days for status updates and more news from GLAST.

GLAST Blog Welcome Message

Welcome to the GLAST Project Scientist Blog!

There are many people around the world interested in the progress of the GLAST mission, and we will post status updates here.  Please check back often.

I plan to include frequent “guest” postings from some of the many scientists, engineers, and others from around the world who make GLAST possible. 

First, what is GLAST?

GLAST is the Gamma-ray Large Area Space Telescope.  NASA’s GLAST mission is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S. 

Please have a look at our mission website, and links therein, for information about the mission and a great media gallery.  There aren’t many times in a scientific career when such a large leap in capabilities is made in a single step, and we’re very excited about what GLAST will soon reveal to us about the Universe. 

What is GLAST doing now?

Since the dramatic and very successful launch on 11 June at 12:05 PM EDT to a circular orbit 565 km above the Earth, the GLAST team at the Mission Operations Center has been working around the clock to check out all the functions of the spacecraft.  About two weeks after launch, we will turn on the two beautiful GLAST instruments: the Large Area Telescope (LAT) and GLAST Burst Monitor (GBM).  More about these activities and the instruments in future posts. 

Things are going very well thus far, and there is much more to do (we have not opened the champagne yet!).  Here is a quick recap of the activities since the launch: 

  • Thursday 12 June.  Routine communications are established, and the observatory is operating in a very stable manner.  All spacecraft navigational systems are powered on, and solar array drive checked out.
  • Friday 13 June.  The star tracker system (small telescopes on the side of the spacecraft that help determine the orientation of the observatory by automatically recognizing patterns of bright stars) is initialized and functioning well, after some very efficient and clever detective work by the mission team to solve an initial configuration mismatch.
  • Saturday 14 June.  The observatory transitions from a pointed observing mode (staring in one direction all the time) to survey mode (sweeping the boresight of the instruments across the sky) — a beautiful ballet maneuver!  To accomplish this, many things must work together in a coordinated way, and this is a great milestone in the early operations checkout.
  • Sunday 15 June – Monday 16 June. Maneuvering exercises and calibrations.  GLAST changes its orientation (aka “slews”) by changing the rotation speeds of four onboard wheels, called reaction wheels.  The onboard computer coordinates these speed changes with the orientation of the solar arrays, all the time monitoring the position on the sky using GPS (the Global Position System, which GLAST uses for both position and time information), the star trackers, and special gyroscopes.

What’s next for GLAST? 

Slew maneuver exercises will continue until Wednesday, when GLAST’s main science data antenna will be turned on and checked out. 

Peeking further ahead, you can find an overview of the first year science timeline here.  We’re really looking forward to this!