Hubble Space Telescope

The Hubble Space Telescope (HST) is a NASA 2.4-meter reflector telescope in space. Instruments:

• WFC3 ("Wide Field Camera 3") with facilities for optical and infrared spectrography, replaced earlier WF/PC and WF/PC2.
• COS ("Cosmic Origins Spectrograph") replaced earlier COSTAR.
• ACS ("Advanced Camera for Surveys") replaced earlier FOC.
• STIS ("Space Telescope Imaging­ Spectrograph") replaced earlier FOS.
• NICMOS ("Near-infrared Camera and Multi-object Spectrometer") replaced the earlier GHRS, but has not been used since 2008 due to an unresolved malfunction.

The PCS ("Pointing Control System") is made up of instruments of the following types:

• FGS ("Fine Guidance Sensors") can also be used for astrometry.
• CSS ("Coarse Sun Sensors").
• MSS ("Magnetic Sensing Systems").
• RSU ("Rate Sensor Units").
• FHST ("Fixed Head Star Trackers").

The optical telescope assembly (OTS) is basically the telescope itself up to the instruments, including the mirrors, baffles and optical shields, locations for instruments, and the frame supporting these in place.

HST was launched in 1990, serviced and upgraded by astronauts (replacing instruments) a number of times, the final occasion in 2009. It remains in operation in 2024 with hopes of continuing for a decade or more. Initial instruments:

• WF/PC ("Wide Field and Planetary Camera").
• GHRS (aka HRS, "Goddard High Resolution Spectrograph").
• HSP ("High Speed Photometer").
• FOC ("Faint Object Camera").
• FOS ("Faint Object Spectrograph").

As launched, the optics were flawed and a system to compensate called COSTAR (Corrective Optics Space Telescope Axial Replacement) was developed and installed in 1993. COSTAR required an instrument bay and HSP was removed to provide that space. Each of HST's current instruments has a correcting mechanism built in and COSTAR was removed in 2009.