FAQs
Q&A ON THE GLAST MISSION
"WHAT DOES GLAST" STAND FOR? Gamma-ray Large Area Space Telescope
WHAT IS THE PURPOSE OF THE GLAST MISSION?
The Universe is home to numerous exotic and beautiful phenomena, some of which can generate inconceivable amounts of energy. GLAST will open this high-energy world. Astronomers will have a superior tool to study how black holes, notorious for pulling matter in, can accelerate jets of gas outward at fantastic speeds. Physicists will be able to search for signals of new fundamental processes that are inaccessible in ground-based accelerators and observatories.
WHAT ARE GLAST'S MAIN MISSION OBJECTIVES?
- To understand the mechanisms of particle acceleration in active galactic nuclei (AGNs), neutron stars, and supernova remnants (SNRs).
- Resolve the gamma-ray sky: characterize unidentified sources and diffuse emission.
- Determine the high-energy behavior of gamma-ray bursts (GRBs) and variable sources.
- Probe dark matter and the early Universe.
WHAT KINDS OF THINGS WILL GLAST STUDY?
- Blazars and Active Galaxies + Learn more
- Gamma-ray Bursts + Learn more
- Neutron Stars + Learn more
- Cosmic Rays and Supernova Remnants + Learn more
- Milky Way Galaxy + Learn more
- The Gamma-ray Background + Learn more
- The Early Universe + Learn more
- Solar System: Sun, Moon, and Earth + Learn more
- Dark Matter + Learn more
- Testing Fundamental Physics + Learn more
- Unidentified Sources and the Unknown + Learn more
GLAST is the first imaging gamma-ray observatory to survey the entire sky every day and with high sensitivity. It will give scientists a unique opportunity to learn about the ever-changing Universe at extreme energies. GLAST will detect thousands of gamma-ray sources, most of which will be supermassive black holes in the cores of distant galaxies. GLAST uses Einstein's principle of E = mc 2 to convert gamma rays into matter in order to track their cosmic origins. GLAST observations may reveal signatures of new physics, including the potential to identify the unknown particle which may compose dark matter.
WHAT ARE SOME OF THE QUESTIONS GLAST HOPES TO ANSWER?
How do black holes accelerate jets of material to nearly light speed? What is the mysterious dark matter? What mechanism produces the stupendously powerful explosions known as gamma-ray bursts? How do solar flares generate high-energy particles? How do pulsars work? What is the origin of cosmic rays? What else out there is shining gamma rays?
WHAT ARE GAMMA RAYS?
Gamma rays are the highest-energy forms of light in the electromagnetic spectrum
WHAT PREVIOUS MISSIONS DOES GLAST CONTINUE AND IMPROVE UPON?
GLAST follows in the footsteps of NASA's Compton Gamma-ray Observatory (CGRO) EGRET and BATSE instruments, which were operational between 1991 and 1999. GLAST will have a field of view and sky survey twice as large as that of the CGRO, and a sensitivity more than 30 times greater than Compton 's EGRET instrument. GLAST will also improve upon the BATSE instrument.
WHAT'S THE DIFFERENCE BETWEEN SWIFT AND GLAST?
Both missions look at gamma-ray bursts (GRBs), but in different ways. Swift can rapidly and precisely determine the locations of GRBs and observe their afterglows at X-ray, ultraviolet, and optical wavelengths. GLAST will provide exquisite observations of the burst over the gamma-ray spectrum, giving scientists their first complete view of the total energy released in these extraordinary events. Beyond GRB science, GLAST is a multipurpose observatory that will study a broad range of cosmic phenomena. Swift is also a multipurpose observatory, but was built primarily to study GRBs.
HOW BIG IS THE SPACECRAFT?
It is 9.2 feet high by 8.2 feet in diameter when stowed, where it is just under the 9-foot diameter allowed in the fairing. GLAST becomes a little bit taller and much wider after it is launched into space, when the Ku-band antenna deploys and the solar arrays are extended.
HOW LONG WILL THE MISSION LAST?
GLAST is expected to operate for a minimum of five years, but has a goal to operate 10 years.
WHERE WILL DATA ANALYSIS HAPPEN?
Around the world. Data analysis will be supported by GLAST's international science team and by the mission's science center, located at NASA's Goddard Space Flight Center (GSFC). The LAT Instrument Science Operations Center (ISOC) is located at Stanford Linear Accelerator Center , Menlo Park , Calif. The (GBM) Instrument Operations Center is located at the National Space Science and Technology Center (NSSTC) in Huntsville, Ala.
WHAT DOES GLAST MEAN TO THE AVERAGE PERSON?
The Universe looks remarkably different outside the narrow range of colors we can see with our eyes. GLAST's spectacular high-energy gamma-ray "eyeglasses" will reveal hidden wonders, opening our minds to new possibilities and discoveries, expanding our understanding of the Universe and our place in it. These new perspectives help us to think differently as well as inspire new generations of students.
GLAST WILL STUDY THE ORIGIN OF COSMIC RAYS. HOW DO COSMIC RAYS AFFECT US?
Although you may never yourself be bombarded by a primary cosmic ray (we are shielded from them by Earth's atmosphere), we are bombarded all the time by the secondary cascades of particles that are created when cosmic rays interact with Earth's atmosphere. These secondary particles are not as energetic, but they provide a constant background radiation to which we are all constantly exposed. Spacecraft and high-altitude planes certainly feel their effects. With the high energy of primary cosmic rays concentrated in such a small bundle, they can disrupt computer hardware or sensitive electronics and these instruments have to be shielded in vehicles traveling above the atmosphere.
WHAT DOES GLAST COST?
U.S. contribution $600 million; international contribution $90 million; Total $690 million.
WHERE IS GLAST'S ORBIT AND WHY IS GLAST IN THIS ORBIT?
Although gamma rays can travel across the Universe to give us their information, they cannot penetrate even the thinnest part of Earth's upper atmosphere. Therefore the detectors need to be placed above the atmosphere. To accomplish this, GLAST will be launched into circular orbit around Earth at an altitude of about 560 km ( 350 miles ). This is a low-Earth orbit. This orbit is chosen to minimize the effects of charged particles that surround Earth, and which would create additional unwanted background signals in the detectors, while still ensuring the full mission lifetime. At that altitude, the observatory will circle Earth every 90 minutes. In sky-survey mode, GLAST will be able to view the entire sky in just two orbits, or about 3 hours.
WHAT DO PROJECT SCIENTISTS DO?
The primary role of the Project Scientist is to provide the scientific leadership necessary to assure that the mission implementation will meet or exceed the scientific requirements. The Project Scientist and her/his deputies are integral members of the Project management team. To accomplish these goals, the Project Scientist functions include: providing scientific oversight of all elements of the mission, reviewing and recommending approval or disapproval of proposed modifications to the science requirements or to the instruments, acting as the primary science interface between the science community and the project, and a ssuring public dissemination of scientific results through professional groups, peer reviewed publications, conferences, workshops, and the relevant public-affairs offices.
INSTRUMENTS:
WHAT ARE THE NAMES OF THE GLAST INSTRUMENTS*?
- Large Area Telescope (LAT)
- GLAST Burst Monitor (GBM)
The LAT detects gamma rays by using Einstein's famous E = mc2 equation in a technique known as pair production. When a gamma ray, which is pure energy, slams into a layer of tungsten in the detector, it can create a pair of subatomic particles (an electron and its antimatter counterpart, a positron). The direction of the incoming gamma ray is determined by projecting the direction of these particles back to their source using several layers of high-precision silicon tracking detectors. A separate detector, called a calorimeter, absorbs and measures the energy of the particles. Since the energy of the particles created depends on the energy of the original gamma ray, counting up the total energy determines the energy of that gamma ray. Because the LAT in orbit is bombarded by many more particles than gamma rays, it wears a "hat" – a third detector that produces a signal when a particle, but not a gamma ray, goes through it. The combination of no signal in this outer detector ("the dog that did not bark"), plus an electron-positron pair of tracks created inside the LAT, signals a gamma ray. Working one gamma ray at a time, the LAT will make gamma-ray images of astronomical objects, while also determining the energy for each detected gamma ray.
Image right: One of the Large Area Telescope towers, which is composed of a stack of interleaved planes of silicon strips and tungsten converters. The LAT has 16 of these towers in a 4x4 array. Credit: NASA+ view high resolution image
WHO HELPED CREATE THE LAT?
The U.S. Department of Energy (DOE) and NASA partnered on the building of the Large Area Telescope (LAT), the primary instrument on GLAST. There were major contributions from France, Italy, Japan, and Sweden. The laboratory that managed the construction of the LAT is the Stanford Linear Accelerator Center, a DOE-funded lab, located at and managed by Stanford University. Although the LAT is the work of literally hundreds of scientists and technicians, the individual who contributed the most to the original design is Bill Atwood, now at the University of California, Santa Cruz.
The LAT was tested extensively during the summer of 2006 at the U.S. Naval Research Laboratory in Washington, D.C. LAT hardware was also used in beam tests at the European Center for Nuclear Research (CERN) and the German Heavy Ion Facility (GSI). The LAT was shipped to the General Dynamics facility in Arizona for integration onto the spacecraft bus. The General Dynamics spacecraft bus provides the power, data, and pointing resources that will enable the LAT to perform its survey of the Universe. Subsequent to the mechanical integration, the command, data, and power interfaces between the instrument and the spacecraft were tested rigorously to insure the compatibility of this spaceflight hardware that had been manufactured all around the globe.
WHAT DOES THE GLAST BURST MONITOR (GBM) DO?
The GLAST Burst Monitor (GBM) was selected as a complementary instrument for the GLAST mission and will be sensitive to X rays and gamma rays with energies between 8 keV and 30 MeV.
WHO HELPED CREATE THE GBM?
The development of the GLAST Burst Monitor and analysis of its observational data is a collaborative effort between the National Space Science and Technology Center in the U.S. and the Max Planck Institute for Extraterrestrial Physics (MPE) in Germany.
HOW WILL THE INSTRUMENTS WORK TOGETHER?
The GBM has an even larger field of view than the LAT. The GBM can see all directions at once, except for the area where Earth blocks its view. When the GBM detects a bright gamma-ray burst, it immediately sends a signal to the LAT to observe that area of the sky. It will do this if it is not already in the field of view, and if it is permissible to move there due to logistical constraints.
WHAT'S A "GEE-WHIZ FACT" ABOUT THE TECHNOLOGY?
The LAT is a 3-ton detector with almost a million channels of electronics, but it uses less than half the power of an ordinary hair dryer.
LAUNCH / DATA:
WHEN AND WHERE IS THE LAUNCH SCHEDULED?The launch is scheduled for 2008 from Cape Canaveral Air Station, on Florida's east coast. GLAST will be carried on a Delta II Heavy launch vehicle.
WHEN ARE THE FIRST RESULTS EXPECTED?
The observatory is activated and tested in the first 60 days after launch. Basic "first light" results may come by day 90.
WHAT WILL THE GLAST IMAGES LOOK LIKE?
GLAST images will typically be intensity gamma-ray maps, often with different colors representing different energy ranges. These maps will be either a small number of individual sources, or as much as the entire sky. There will also be information about energy spectra and timing in some cases. An example of a simulated GLAST sky is shown below.
Image above: Simulated GLAST Sky after one year of operation. Credit: S.W. Digel (NASA/GSFC)
+ view high resolution image
HOW WILL THE DATA BE DISTRIBUTED?
The data will be made available over the Internet from the GLAST Science Support Center (GSSC) at NASA's Goddard Space Flight Center.
HOW AND WHERE WILL THE DATA BE PROCESSED?
Data analysis will be performed at two remote science centers, located at the Stanford Linear Accelerator Center, operated by Stanford University for the U.S. Dept. of Energy, and at NASA's Marshall Space Flight Center, in Huntsville, Alabama. GLAST data goes to the GSSC and is then distributed to the science community.
WHERE WILL MISSION OPERATIONS BE?
Mission operations will be performed from facilities at NASA Goddard Space Flight Center.
WILL THE GLAST MISSION BE RENAMED AFTER LAUNCH?
Yes. GLAST will receive a new name once it is in orbit.
WHO CAN HELP WITH PRESS RELEASES, INTERVIEWS, OTHER RESOURCES? VIDEO?
NASA and Sonoma State public-affairs officers can provide the latest press releases, breaking news, video, and arrange interviews. At Sonoma State University, contact Lynn Cominsky, Education and Public Outreach, Tel. 707-664-2655, Email: lynnc@universe.sonoma.edu . At NASA Goddard Space Flight Center, contact: Rob Gutro, Public Affairs Officer, Tel. 301-286-4044 or by email Robert.J.Gutro@nasa.gov or Robert Naeye, Science Writer, Tel. 301-286-4453, rnaeye@milkyway.gsfc.nasa.gov . Video and animation requests should be directed to Liz Smith at NASA-TV. Tel. 301-286-1540, Liz.Smith@nasa.gov .
WHO CAN HELP WITH LAUNCH SUPPORT IN PUBLIC AFFAIRS?
George Diller will provide public-affairs launch support from Kennedy Space Center, Fla. Tel. 321-861-7643 Email: george.h.diller@nasa.gov . The GLAST launch will occur from Cape Canaveral Air Station, adjacent to the Kennedy Space Center.
PARTNERS:
WHO ARE THE PARTNERS INVOLVED WITH THE MISSION?
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.
PARTNERS ON GLAST HARDWARE INCLUDE:
- French Institutions
Centre National d'Études Spatiales (CNES)
Commissariat à l'Energie Atomique, Département d'Astrophysique (CEA/DAPNIA), de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée,
Institut National de Physique Nucléaire et de Physique des Particules, IN2P3
Laboratoire de Physique Théorique et Astroparticules, Montpellier, GAM (IN2P3/LPTA)
Laboratoire Leprince-Ringuet de l'École Polytechnique (IN2P3/LLR)
- German Institution
- Italian Institutions
Italian Space Agency (ASI)
Istituto di Fisica Cosmica, Milano, CNR
INFN and University of Bari
INFN and University of Padova
INFN and University of Perugia
INFN and University of Pisa
INFN and University of Rome 2
INFN and University of Trieste
INFN and University of Udine
- Japanese Institutions
Tokyo Institute of Technology
Institute for Cosmic-Ray Research (ICRR)
Institute for Space and Astronautical Science (ISAS)
Hiroshima University
- Swedish Institutions
Stockholms Universitet
- U.S. Institutions
NASA Goddard Space Flight Center, Laboratory for High Energy Astrophysics
NASA Marshall Space Flight Center
Ohio State University, Physics Department
Sonoma State University, NASA Education and Public Outreach Group
Stanford University (SU), Physics Department
Stanford University, Hansen Experimental Physics Laboratory (HEPL) and Kavli Institute for Particle Astrophysics and Cosmology (KIPAC)
Stanford University, Stanford Linear Accelerator Center (SLAC)
Texas A&M University-Kingsville
University of Alabama in Huntsville
University of California at Santa Cruz, Physics Department; SCIPP
University of Washington
U.S. Department of Energy
U.S. Naval Research Laboratory, High Energy Space Environment (HESE) branch
WHAT WERE THE CONTRIBUTIONS OF THE FRENCH PARTNERS?
They designed and built the support structure for the Calorimeter.
WHAT WERE THE CONTRIBUTIONS OF THE GERMAN PARTNER?
The Max Planck Institute built all of the sensors and the power-supply box and support on the GLAST Burst Monitor (GBM) instrument. One of its scientists is the GBM Co-principal Investigator.
WHAT WERE THE CONTRIBUTIONS OF THE ITALIAN PARTNERS?
They provided particle physics and astrophysics expertise and physically built the LAT Tracker.
WHAT WERE THE CONTRIBUTIONS OF THE JAPANESE PARTNERS?
They provided oversight in the making of the silicon-strip detectors in the LAT Tracker.
WHAT WERE THE CONTRIBUTIONS OF THE SWEDISH PARTNERS?
They provided sensors for the LAT Calorimeter.
WHAT WERE THE CONTRIBUTIONS OF NASA GODDARD SPACE FLIGHT CENTER?
NASA Goddard managed and built the Anticoincidence Detector (ACD). The overall GLAST Program Mission Management and Mission Systems Engineering is provided by NASA Goddard. In addition, the Mission Operations Center (MOC) and the GLAST Science Support Center (GSSC) were provided by and are located at NASA Goddard.
WHAT WERE THE CONTRIBUTIONS OF NASA KENNEDY SPACE CENTER?
NASA's Launch Services Program office at the Kennedy Space Center (KSC) is responsible for countdown management of the Delta II rocket for GLAST. KSC is also responsible for the integration of GLAST with the Delta II, provides ground support necessary for final GLAST spacecraft preparations. The Delta II is provided to NASA as a launch service by the United Launch Alliance. The spacecraft will launch from Space Launch Complex 17 at Cape Canaveral Air Force Station.
WHAT WERE THE CONTRIBUTIONS OF NASA MARSHALL SPACE FLIGHT CENTER?
It provided the Data Processing Unit and instrument integration and testing. The management of the GLAST Burst Monitor (GBM) instrument is done through the National Space Science and Technical Center, out of NASA Marshall, Huntsville, Ala. Charles Meegan is the GBM Principal Investigator.
WHAT WERE THE CONTRIBUTIONS OF THE NAVAL RESEARCH LABORATORY?
It managed the building of the Calorimeter.
WHAT WERE THE CONTRIBUTIONS OF THE OHIO STATE UNIVERSITY?
It provided particle physicists, and helped with trigger and data system, including the algorithms on-board.
WHAT WERE THE CONTRIBUTIONS OF SONOMA STATE UNIVERSITY?
It provides management of education and public outreach.
WHAT WERE THE CONTRIBUTIONS OF STANFORD UNIVERSITY?
It is the lead on the Large Area Telescope (LAT). Peter Michelson is the LAT Principal Investigator. Stanford managed the LAT and hosts the Instrument Science Operations Center (ISOC) at the Stanford Linear Accelerator Center. The ISOC is where all the raw data from the LAT is processed and made ready for scientific analysis. The data is sent to the GLAST Science Support Center at NASA GSFC from where it is distributed to the scientific community.
WHAT WERE THE CONTRIBUTIONS OF THE UNIVERSITY OF CALIFORNIA, SANTA CRUZ?
It provided management of the Tracker in the LAT.
WHAT WERE THE CONTRIBUTIONS OF THE UNIVERSITY OF WASHINGTON?
It provided software support.
WHAT WERE THE U.S. DEPARMENT OF ENERGY'S (DOE) AND SLAC'S CONTRIBUTIONS?
The Large Area Telescope (LAT) is managed at the U.S. DOE Stanford Linear Accelerator Center (SLAC), a U.S. DOE lab. SLAC was responsible for the overall design and development of the LAT.
WHO IS RESPONSIBLE FOR BUILDING THE ACTUAL SPACECRAFT?
General Dynamics Advanced Information Systems, Gilbert, Arizona.
WHAT DOES THE SCIENTIFIC COMMUNITY THINK OF THE GLAST MISSION?
The National Academies of Sciences ranked GLAST as the top-priority mid-sized project in its 2000 Decadal Survey of Astronomy and Astrophysics.
Image above: Old version of the GLAST logo. Credit: NASA