1999-011A
The Wide Field IR Explorer (WIRE) is SMEX 5. PI was Perry Hacking of JPL. The cryogenically cooled satellite would carry out IR studies of galaxy formation. The telescope had a 33 arcmin FOV and 12 and 25 micron detectors, with 20 arcsec resolution. It will survey 1000 square deg. Spacecraft mass is 187 kg. The Lockheed Martin cryostat is cooled to 6.5K by solid hydrogen. The spacecraft uses the GSFC SMEX bus with an octagonal structure.
WIRE was launched by a Pegasus rocket from Vandenberg. The Pegasus was successful, although a guidance anomaly caused delays to the next Pegasus flight. WIRE was deployed in a 539 x 593 km x 97.5 deg sun-synchronous orbit.
Unfortunately, the telescope cover was ejected shortly after orbit injection (instead of 3 days later), before the satellite was stabilized. Earthlight entering the aperture boiled off hydrogen, sending the spacecraft tumbling at 1 rev per second. For several days battery power decreased and the hydrogen vented, with the last hydrogen depleted in a few days. The spin was controlled by Mar 12.
The failure investigation reported that a circuit in the satellite's power system surged when it was switched on, and triggered the explosive bolts on the cover.
After the tumbling craft was brought back under control it seemed that it could only be used for engineering tests. Then Derek Buzasi of Berkeley realized that WIRE's star tracker, designed to point the observatory at its targets, was itself a useful optical space telescope. With only a 2-inch aperture, the F/1.8 telescope poses no challenge to Hubble, but its CCD detector can take low resolution images ten times a second and has remarkable photometric accuracy. WIRE's star tracker can measure a bright (0-2mag) star to within a millimagnitude in each exposure, and Buzasi is interested in studying small amplitude oscillations in convective stars, something WIRE's tiny space telescope can do more efficiently than a large ground based telescope like Keck. On April 30 WIRE was turned to observe Procyon as a test target, and followed up with the Ap star Gamma Aquilae, confirming its known variations. A long look at Regulus confirmed its constancy to a few micromagnitudes, showing that WIRE's observations were reliable. The main science program started in May with the target Alpha Ursae Majoris. Operations continued until funding ended in Sep 2000; a second cycle of observations began in 2003 and was concluded in 2008.
| WIRE | |||
| Date | Time | Event | Orbit |
|---|---|---|---|
| 1999 Mar 1 | 0155 | L-1011 T/O from VAFB | |
| 0256 | Abort at T-45s, fin pin problem | ||
| 0324 | L-1011 landed at VAFB | ||
| 1999 Mar 5 | 0155 | L-1011 T/O from VAFB | |
| 0255:55 | Launch from L-1011 | ||
| T+0:05 St 1 burn | |||
| T+1:15 St 1 burnout | |||
| T+1:31 St 2 burn | |||
| T+2:06 Fairing | |||
| T+2:43 St 2 burnout | |||
| 0307:29 | T+7:34 St 3 burn 68s | ||
| 0308:37 | T+8:42? St 3 burnout | ||
| 0309:37? | T+9:42? St 3 sep | ||
| 0327 | Cryo cover ejected prematurely | ||
| Venting H | |||
| 1999 Mar 8 | Cryo depleted | 95.99 539 x 593 x 97.5 | |
| 1999 Mar 12 | Spacecraft stable in safemode | ||
| 1999 Apr 30 | Star camera observations begin | ||
| 2000 Sep 30 | Star camera operations suspended | ||
| 2003 Nov 26 | Star camera operations resume | ||
| 2003 Dec 16 | Observing program begins | ||
| 2004 Jan | Control to Bowie State, MD | ||
| 2008 Mar? | End of operations | ||
Payload:
- Solid hydrogen cryostat.
- Telescope, Ritchey-Chretien 0.30m.
- Focal plane arrays, 12 and 25 mu, 128 x 128 pixels
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