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The Galaxy Evolution Explorer (GALEX) is an orbiting space telescope that will observe galaxies in ultraviolet light across 10 billion years of cosmic history. Such observations will tell scientists how galaxies, the basic structures of our Universe, evolve and change. Additionally, GALEX will probe the causes of star formation during a period when most of the stars and elements we see today had their origins.
Led by the California Institute of Technology, GALEX will conduct several first-of-a-kind sky surveys, including an extra-galactic (beyond our galaxy) ultraviolet all-sky survey. During its 29 month mission GALEX will produce the first comprehensive map of a Universe of galaxies under construction, bringing us closer to understanding how galaxies like our own Milky Way were formed.
GALEX will also identify celestial objects for further study by ongoing and future missions. GALEX data will populate a large, unprecedented archive available to the entire astronomical community and to the general public.
Scientists would like to understand when the stars that we see today and the chemical elements that make up our Milky Way galaxy were formed. With its ultraviolet observations, GALEX will fill in one of the key pieces of this puzzle.
MISSION NAME: Galaxy Evolution Explorer (GALEX), a NASA small explorer class mission.
OBJECTIVE: To map the history and evolution of the Universe, 80 percent of the way back to the Big Bang. GALEX aims to answer the questions:
1. What is the history of star formation in the Universe?
2. What do nearby galaxies look like in ultraviolet light?
3. When and where did the stars and elements we see today have their origins?
LAUNCH DATE: GALEX was launched at 8am EDT (5am PDT) on April 28th, 2003.
MISSION DURATION: 29 months.
LAUNCH SITE: Cape Canaveral, Kennedy Space Center, Florida.
LAUNCH VEHICLE: Air launched Pegasus XL. Carried by an L-1011 Stargazer aircraft to 40000 feet over the Atlantic Ocean.
ORBIT: Near circular, altitude 694 x 700 km, eccentricity 0.00045, inclination to the equator 28.99 degrees. Right Ascension of the Ascending Node is 118.23 degrees.
SATELLITE MASS: 280 kilograms (a little more than 617 pounds).
TELESCOPE: f/6.0 Richey-Chrétien design, 50 centimeter (19.7 inches) diameter primary mirror, 22 centimeter (8.8 inches) diameter secondary mirror.
DETECTORS: Two 65 millimeter (2.5 inches) diameter, microchannel plate detectors. Far ultraviolet sensitive to light with wavelengths 135 to 175 nanometers. Near ultraviolet sensitive to light with wavelengths 175 to 280 nanometers.
OBSERVING TIMELINE: Dayside of the Earth: no science observations, solar panels aligned to face the Sun. Twilight: slew to science target. Night: science data collection while spacecraft is in Earth's shadow.
DATA PRODUCTS: Circular images of the sky with 1.2 degree diameter and 5 arcsecond resolution in two ultraviolet light bands. Spectra with 10 to 20 Angstrom resolution of all objects in the field of view obtained using a grism in the light path.
TELEMETRY SYSTEM: X-band science downlink has 25 Megabits per second transmission. S-band command and housekeeping data link, 2 Megabits per second transmission.
GROUND STATIONS: South Point, Hawaii, and Dongara, Australia. Tracking and Data Relay Satellite (TDRS) communications system capable.
SOLAR ARRAYS: Fixed, Gallium Arsenide solar cells with total area of 3 square meters (27 square feet).
POWER SUPPLY: Orbit average of 290 watts.
CONSUMABLES: No consumable fuel needed on orbit.
SPACECRAFT ATTITUDE CONTROL: 3-axis stabilized. Two gyroscope systems; a hemispherical resonating gyroscope and a ring laser gyroscope. Pointing stability from four reaction wheels and magnetic torquer bars and coil. Pointing direction determined using a Sun sensor and a star tracker.
SPACECRAFT BUS: Built by Orbital based on the OrbView4 satellite design.
PRINCIPAL INVESTIGATOR: Professor Chris Martin, California Institute of Technology.
PROJECT MANAGER: Jim Fanson, Jet Propulsion Laboratory.
MISSION OPERATIONS MANAGER: Kerry Erickson, Jet Propulsion Laboratory.
MAJOR CONTRACTORS/CONTRIBUTORS:
* California Institute of Technology
* Jet Propulsion Laboratory
* Orbital
* Johns Hopkins University
* Laboratoire d'Astronomie Spatial, France
* Yonsei University, South Korea
* University of California, Berkeley
* Goddard Space Flight Center
* Kennedy Space Center
* Space Telescope Science Institute |
