The Universe in Gamma Rays - Comprehensive presentation of field research, deals with astronomical results, including the surprising result that the gamma-ray sky is continuously changing.
What Are Gamma Rays? Gamma Rays are a type of electromagnetic radiation, like optical light or radio waves. Electromagnetic (em) waves have a wide range of wavelengths and they can be used to see different views of objects. Visible light only shows us what is on the surface, but other types of em waves can reveal more, like the x-rays used by doctors to see broken bones. In their quest to understand our universe, astronomers long ago branched out from visible light to examine objects that radiate in the microwave and x-ray wavelengths. However, gamma rays, the most energetic kind of EM wave have remained difficult to use until now, as there are very few strong sources for astronomers to view.
The world's most sensitive Gamma Ray telescopes are being inaugurated in Namibia (in Southwest Africa) on September 3rd. The High Energy Stereoscopic System (H.E.S.S.), a European/African collaboration in which the UK is a partner, will look for Gamma Rays produced by the most energetic particles in the Universe. The array initially consists of four telescopes, the first of which will become operational next week. This one telescope alone is more sensitive than any other existing ground-based array or telescope working in this particular area of the electromagnetic spectrum.
Once all four telescopes are operational in late 2003, researchers from the University of Durham will use H.E.S.S. to investigate a range of extreme cosmic environments such as the supernova remnants formed when a star dies. A major goal is to see if these are a source of cosmic rays - charged particles that constantly bombard the Earth from space. The origin of cosmic rays is difficult to determine as they are influenced by the magnetic field of our Galaxy. However, the Gamma Rays they emit travel in a straight line, so they may reveal the primary source of the cosmic rays. H.E.S.S. will also be probing the structure of pulsars (rapidly rotating stars formed when a massive star explodes at the end of its life, which emit pulses across the range of the electromagnetic spectrum) and active galactic nuclei to find the source of their energy.
Dr Paula Chadwick, of the Durham team, explains: "H.E.S.S. is set to give us unique insights into some of the most extreme environments in the universe. We have some expectations about what we will be able learn more about - supernova remnants, active galaxies and so on - but experience tells us that when you improve the sensitivity of your telescope, you see things you never expected as well. It's going to be very exciting!"
When Gamma Rays are absorbed by the Earth's atmosphere, pairs of electrons and positrons are created and emit tiny flashes of light in a process known as Cherenkov radiation. Telescopes such as H.E.S.S can detect these tiny flashes of light. By using the Earth's atmosphere as part of the detector, the telescopes have much greater sensitivity than an equivalent space based device, and can detect far fainter Gamma Ray sources than previously possible.
Gamma rays are usually produced by particles moving very rapidly. The study of Gamma Rays enables astronomers to learn more about systems that accelerate these particles, such as active galactic nuclei where supermassive black holes produce jets of particles travelling near the speed of light. These are strong and highly variable sources of gamma rays. Gamma Rays can also be produced by the annihilation of massive particles that may be the source of the 'missing mass' in the universe.
The University of Durham' s role in the design and manufacture of HESS has been in calibrating the camera that will record the Cherenkov radiation and in developing systems that will measure the atmospheric conditions. This is critically important as variations in the atmosphere, such as cloud cover, can dramatically reduce the amount of light reaching the telescopes. The Durham scientists are now working on various refinements to calibration systems, and a more efficient mirror making technique that they hope to use when the array is extended from the current 4 telescopes to the planned 12 or 16.
Namibia is an excellent site scientifically, one of the best in the world for ground-based optical astronomy and with ideal atmospheric conditions for the techniques used by H.E.S.S. However, practically it has represented a huge challenge with limited road access to the site and water, power and computing connections having to be put in place specially.
June 6, 2001 - Lockheed Martin Space Systems one of two selected for spacecraft design analysis on NASA's Gamma-ray Large Area Space Telescope
Lockheed Martin Space Systems is one of two contractors selected by the NASA Goddard Space Flight Center in Greenbelt Md. to perform its spacecraft accommodation study for the Gamma-ray Large Area Space Telescope (GLAST) Observatory. Planned for launch in 2006, GLAST will inaugurate a new epoch in space-based physics investigation.
"We're extremely proud as a company to have been given the opportunity to develop a design for GLAST that optimizes science return through a precise understanding of all the interfaces between the spacecraft and the scientific instruments," said Dr. Domenick Tenerelli, Space Systems program manager for GLAST. "A mission that seeks to understand the most energetic events in the cosmos is particularly exciting. We're delighted to be working with NASA Goddard to develop a low-risk, low-cost design for this fundamental mission to better understand the structure and evolution of the universe."
The Space Systems design will incorporate the LM 900 bus, used on the IKONOS commercial remote sensing spacecraft built for Space Imaging of Thornton, Co. The LM 900 is an ideal spacecraft for GLAST's two main instruments, the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The LM 900 provides a platform that meets or exceed all requirements for command and data handling, power distribution, pointing and control, telecommunications, software interfaces, thermal interfaces and structural integrity.
Additionally, Space Systems brings to the table a long commitment to space science. The company has provided spacecraft, as well as systems engineering, integration, and test, for the Hubble Space Telescope, Lunar Prospector, Imager for Magnetopause to Aurora Global Exploration, Gravity Probe-B, the Space Infrared Telescope Facility, and the Space Interferometry Mission. Design concepts for NASA's Next Generation Space Telescope and the Terrestrial Planet Finder are also in progress at the Space Systems facility in Sunnyvale.
GLAST will identify and study nature's high-energy particle accelerators through observations of active galactic nuclei, pulsars, stellar-mass black holes, supernova remnants, gamma-ray bursts, diffuse galactic and extragalactic high-energy radiation, and mysterious unidentified gamma-ray sources. GLAST will use these sources to probe important physical parameters of the Galaxy and the Universe that are not readily measured with other observations. The high-energy gamma rays will be used to search for a variety of fundamentally new phenomena, such as particle dark matter and Hawking radiation from evaporating black holes.
The scientific objectives of the GLAST mission require a high-energy gamma-ray telescope with:
Angular resolution sufficient to identify point sources with objects at other wavelengths.
A wide field-of-view that will permit the study of sources that exhibit extreme intensity variations on timescales from seconds to months or longer.
A large effective area to detect a large sample of sources and determine their energy spectra.
New detector technologies that offer significant improvements over existing hardware (a factor of between 10 and 100 improvement in source sensitivity, depending on energy) will allow these requirements to be met well within the cost constraints of an intermediate class astrophysics mission. GLAST is an international collaboration of government agencies from the United States, France, Germany, Japan, Italy, and Sweden. The LAT is a joint project with NASA and the U.S. Department of Energy; and it will be constructed by Stanford University, the Stanford Linear Accelerator Center, the University of California, Santa Cruz, the Naval Research Laboratory, NASA Goddard, and the international partners.
NASA Marshall Space Flight Center, along with the University of Alabama in Huntsville and Germany will build the GBM. The overall mission management resides at NASA Goddard Space Flight Center. Lockheed Martin Space Systems Company, headquartered in Denver, Colo., is one of the major operating units of Lockheed Martin Corporation. Space Systems designs, develops, tests, manufactures, and operates a variety of advanced technology systems for military, civil and commercial customers. Chief products include a full-range of space launch systems, including heavy-lift capability, ground systems, remote sensing and communications satellites for commercial and government customers, advanced space observatories and interplanetary spacecraft, fleet ballistic missiles and missile defense systems.
Headquartered in Bethesda, Md., Lockheed Martin is a global enterprise principally engaged in the research, design, development, manufacture, and integration of advanced-technology systems, products, and services. The Corporation's core businesses are systems integration, space, aeronautics, and technology services. Employing more than 140,000 people worldwide, Lockheed Martin had 2000 sales surpassing $25 billion.