Galex

The Galaxy Evolution Explorer (GALEX) was an orbiting space telescope that was to observe galaxies in ultraviolet wavelengths. Such observations would provide data how galaxies, the basic structures of our Universe, evolve and change. Additionally, GALEX would 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 was to conduct several first-of-a-kind sky surveys, including an extra-galactic ultraviolet all-sky survey.

• 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: What was the history of star formation in the Universe? What do nearby galaxies look like in ultraviolet light? When and where did the stars and elements we see today have their origins?
• MISSION DURATION: 29 months.
• ORBIT: 690 kilometers (428 miles), 29 degree inclination to the equator.
• SATELLITE MASS: 280 kilograms.
• TELESCOPE: f/6.0 Richey-Chretien design, 50 centimeter diameter primary mirror, 22 centimeter diameter secondary mirror.
• DETECTORS: Two 65 millimeter 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 was 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 prism in the light path.
• TELEMETRY SYSTEM: X-band science downlink had 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.
• 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 torque 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

Mass: 280 kg (610 lb). Associated Launch Vehicle: Pegasus XL.

• 2003 April 28 - Galex - Launch Site: Cape Canaveral. Launch Vehicle: Pegasus XL. Mass: 280 kg (610 lb). Perigee: 694 km (431 mi). Apogee: 699 km (434 mi). Inclination: 29.00 deg. Period: 98.70 min.

  Much delayed launch (from January 19, May 19, July 16, 21 and 30, August 14 and October 17, 2002; January 27, March 25 and 30, April 15 and 26 2003).