Hubble Space Telescope

 1990-037B

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The idea of an orbiting space telescope had been proposed by Lyman Spitzer as early as the 1940s. NASA's 3-m aperture Large Space Telescope project was begun in 1972, for a planned launch in 1983. The project was downsized to simple Space Telescope, a 2.4m telescope, and delayed many times. A special institute, the Space Telescope Science Institute (STScI) was opened to run the science aspects of the mission, and it became a well established player on the astronomy research scene even before ST's launch. The telescope was renamed the Edwin P. Hubble Space Telescope Observatory in honor of the astronomer (1889-1953) who discovered the expansion of the Universe. The HST project became a joint mission with the European Space Agency.

HST was built by Lockheed Corp. The spacecraft consisted of the OTA (Optical Telescope Assembly), twin solar arrays which could be adjusted to face the sun, and an instrument bay at the Cassegrain focus. There were four instrument locations at the rear of the telescope, and one bay accessed from the side. The initial set of instruments consisted of the Wide Field/Planetary Camera (WF/PC), which took optical images; the Faint Object Camera (FOC), an ESA instrument which took deep ultraviolet images; the Faint Object Spectrograph (FOS), which took high sensitivity, moderate resolution ultraviolet spectra; the Goddard High Resolution Spectrograph (GHRS), which took very high resolution ultraviolet spectra; and the High Speed Photometer (HSP), which could measure the brightness of stars accurately and with high time resolution. HST also carried three Fine Guidance Sensors which were used to accurately point the telescope, but could also be used for scientific purposes as astrometric instruments.

HST finally got its ride to orbit at 1233:51 on 1990 Apr 24 when Discovery lifted off pad 39B at Kennedy Space Center on mission STS-31R. Main engine cutoff was at 1242 and the orbit was circularized by the OMS 2 burn somewhat later. An RCS thruster burn adjusted Discovery's orbit to 613 x 615 km at 1945. Meanwhile, at 1721 on Apr 24, HST was commanded on. The instruments were activated at 2000, and at 1106 on Apr 25 the RMS arm grappled the HST satellite. It was unberthed at 1245 and held above the payload bay. The solar array masts were deployed at 1432, the High Gain Antenna at 1530, and the port solar array at 1630. The starboard array would not deploy on the first attempt at 1750, but at 1903 it was successfully completed. Hubble Space Telescope was released from the RMS at 1938 and floated free. Its first TDRS contact was at 1837 on Apr 26, and the aperture door was opened at 1348, being fully open by 1403. By the end of the day HST was in software sunpoint mode and ready to begin testing.

It was not long before STScI scientists realized that something was dreadfully wrong. No adequate focus could be found for the telescope. It was later discovered that an incorrect test measurement on the ground had caused mirror manufacturers Perkin-Elmer to grind the mirror to the wrong shape, inducing a spherical aberration. While a small amount of the light from a star was contained within 0.1 arcseconds of its true position, most of it was scattered over a much larger area of the detector. This meant that although HST could be used to do excellent science on isolated point sources just by increasing exposure times, and could do ultraviolet spectroscopy better than any other previous satellite, it could not produce the sharp imaging it was designed to do, and many of the key programs such as measuring the extragalactic distance scale were compromised. Another problem surfaced - the European built solar arrays were flapping as the satellite passed from night into day, causing errors in the pointing accuracy. Nevertheless, observations were begun in late 1990 and soon results were pouring in.

The plan developed to recover from the mirror error was to install a special device called COSTAR in one of the axial bays. Since the HSP was the least used instument, it would be removed to make room for COSTAR. COSTAR would deploy a set of mirrors on booms which would be placed in front of the apertures of the FOS, FOC and GHRS instruments - effectively giving them spectacles. The new mirrors would precisely correct the wavefront and refocus the light. This solution would not work for the radial bay, so development of the second generation WF/PC was accelerated and a corrective lens was added to its design.

The first servicing mission, STS-61 in Dec 1993, removed WF/PC and HSP and installed WF/PC 2 and COSTAR. The astronauts also replaced the solar arrays, repaired the GHRS power supply, and added a computer coprocessor. The first new images from the refurbished HST were made public in Jan 1994 and showed a dramatic improvement in the data.

The second servicing mission added two new instruments: STIS (the Space Telescope Imaging Spectrograph) and NICMOS (the Near Infrared Camera/Multi-Object Spectrograph). One of the NICMOS cameras was compromised when problems with the nitrogen dewar made it run hot.

HST needs three gyros for routine operations, and in 1999 all redundancy was lost. The planned third servicing mission was split into two parts, with SM3A accelerated as an emergency gyro repair mission.

	Launch	SM1	SM2	SM3A	SM3B	SM4
	STS-31	STS-61	STS-82	STS-103	STS-109
Radial +V2	FGS-1		FGS-1R
Radial +V3	FGS-2			FGS-2R		FGS-2RR
Radial -V2	FGS-3
Radial -V3	WFPC	WFPC-2				WFC3
Axial +V3/+V2	FOC				ACS
Axial +V2/-V3	HSP	COSTAR				COS
Axial -V3/-V2	GHRS		STIS
Axial -V2/+V3	FOS		NICMOS		(NCS)

HST ORUs Name	Mass	Size	Manuf.	Loc
Radial Units
WFPC
WFPC2	281	1.0 x 1.3 x 0.5, 2.2	JPL
WFC3	404	1.0 x 1.3 x 0.5, 2.2	Ball/STScI
FGS-1	220	1.0 x 1.6 x 0.5	Perkin-Elmer
FGS-2
FGS-3
FGS-1R S/N2001	220
FGS-2R S/N2002	220
FGS-2RR	210
Axial Units
FOC	318	0.9 x 0.9 x 2.2	ESA/Dornier
HSP	273
GHRS
FOS	326?		Martin Marietta/Denver, UCSD
COSTAR	290	0.9 x 0.9 x 2.2	Ball
STIS	374	0.9 x 0.9 x 2.2	Ball
NICMOS	391	0.9 x 0.9 x 2.2	Ball
ACS	397	0.9 x 0.9 x 2.2	Ball
COS	386	0.9 x 0.9 x 2.2	Ball
Solar Arrays
SA I	160?
SA II Flex	154	12.1 x 3.3m
SA-3 Rigid(SM3B)	290	7.1 x 2.6m
Other components
DF-224 Computer	50	0.4 x 0.4 x 0.3m		SSM ES Bay 1
Adv 486 Computer	32	0.5 x 0.5 x 0.3m	(SM3A)	Bay 1
DMU	38	0.6 x 0.7 x 0.2m		SSM ES Bay 1
DIU (4)	16	0.2 x 0.4 x 0.4m		Bay 3,7,10;OTA ES
ESTR tape rec.(2)	9	0.2 x 0.2 x 0.3m		Bay 5,8
SSR (2) (SM2,3A)	9	0.2 x 0.2 x 0.3m	Bay 5, 8
RWA (4)	45	Ellipsoid 0.6dia 0.3?l	Bay 6 and 9
Oscillator (2)	1	Cyl 0.2l 0.1d		Bay 2
Mag.torquers	45	Cyl 2.5l 0.08d		Ext SSM FS
BMA NiH2 Battery Mod (2)	218	0.9 x 0.9 x 0.3m		Bay 2,3
PCU power control	55	1.1 x 0.3 x 0.2m		Bay 4
PDU (4)	11	0.3 x 0.1 x 0.5m		Bay 4
RGA gyro RSU (3)	11	0.3 x 0.3 x 0.2		SSM
RGA gyro ECU (6)				Bay 10
Primary Mirror	818	2.4 dia		OTA
OTA Main Ring	546	2.9 dia 0.4l		OTA
NCS
SADE drive elec
OTA reaction plate
Focal Plane FPSA	546	2.1 x 3.1m truss		OTA
SI C&DH;	61	0.55 x 0.82 x 0.24
Soft Capture Mech		1.83l 0.61h
NOBL	4.4	1.6 x 1.4

 

HST
Date	Time	Event	Orbit
1990 Apr 24	1233:51	Launch from LC39B
	1721	HST commanded on
	2000	HST instruments activated
1990 Apr 25	1106	RMS grapple HST
	1237	HST on internal power
	1245	HST unberthed
	1432	Solar array masts deployed
	1530	HGA deployed
	1630	Port solar array deploy
	1750	Stbd solar array deploy
	1937:51	HST released
1990 Apr 27	1101	Begin Aperture Door Open sequence
	1229?s	Telescope door open
1997 Feb 11		COSTAR retracted
1997 Feb 13		OV-103 captures HST
1999 May 20		Gyro 3 failed; 1 gyro from safemode