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Fine Guidance Sensor (HST)

From the center to outer edge of the FGS field of view is 14.1 arcminutes[1] This is a diagram of the field of view of each Hubble Space Telescope instrument, including the three FGS instruments (FGS field of view(s) highlighted in yellow)
A Fine Guidance Sensor being refurbished between servicing missions SM3A and SM4
A fine guidance sensors in space on STS Servicing Mission 2 in 1997

Fine Guidance Sensor (FGS) for the Hubble Space Telescope is a system of three instruments used for pointing the telescope in space, and also for astrometry and its related sciences.[2] To enable aiming the telescope at a specific spot in the sky, each FGS combines optics and electronics.[2] There are three Hubble FGS, and they have been upgraded over the lifetime of the telescope by crewed Space Shuttle missions.[3] The instruments can support pointing of 2 milli-arc seconds (units of degree).[4] The three FGS are part of the Hubble Space Telescope's Pointing Control System, aka PCS.[5] The FGS function in combination with the Hubble main computer and gyroscopes, with the FGS providing data to the computer as sensors which enables the HST to track astronomical targets.[6]

The FGS can be used to locate something in space, and then lock-on to it.[7] It can provide the movements the telescope must make to keep the object in view, for the main instruments to record data on.[8]

The FGS were originally made by the optics company Perkin-Elmer, and as removable and repairable instruments it has been possible to refurbish them over the lifetime of the telescope.[8] The first replacement FGS was installed in 1997, swapping out FGS1.[5]

In May 2009, on STS-125 a FGS was replaced during the mission to the Hubble telescope by the Space Shuttle.[9] The astronaut crew performed an EVA (spacewalk) to service the FGS and other components on the telescope in Earth orbit.[9] This was the SM4 mission.[6]

An example of astrometry science with the Hubble FGS system is observations of the Low-Mass Binary star system L722-22.[10] Observations were taken of the system in 1990s, and the data helped determine the mass of each of the components of L722-22, which is also known as LHS 1047 and GJ 1005.[10]

The FGS are white-light shearing interferometers.[5] The FGS weigh 220 kg (485 lb) and have dimensions of roughly 0.5 m × 1.0 m × 1.6 meters.[11]

  1. ^ "Hubble Space Telescope Systems" (PDF). Goddard Space Flight Center, Astrophysics Science Division. p. 20. Retrieved November 27, 2023.
  2. ^ a b "Hubble's Instruments: FGS - Fine Guidance Sensors". www.spacetelescope.org. Retrieved 2017-03-03.
  3. ^ "NASA - Refurbished Fine Guidance Sensor (FGS)". www.nasa.gov. Retrieved 2017-03-03.
  4. ^ Fine Guidance Sensors Aboard the Hubble Space Telescope, the Scientific Capabilities of these Interferometer
  5. ^ a b c "Fine Guidance Sensors". Space Telescope Science Institute. Retrieved November 27, 2023.
  6. ^ a b "NASA - Hubble Space Telescope Servicing Mission 4
    Fine Guidance Sensor"    . www.nasa.gov. Retrieved 2017-03-03.
  7. ^ "Fine guidance sensors: Hubble's unsung heros". NewsTimes. Retrieved 2017-04-12.
  8. ^ a b "Fine guidance sensors: Hubble's unsung heros". NewsTimes. Retrieved 2017-03-03.
  9. ^ a b "Photo Index 1". spaceflight.nasa.gov. Archived from the original on 2009-05-26. Retrieved 2017-03-03.
  10. ^ a b Hershey, John L.; Taff, L. G. (1998-01-01). "Hubble Space Telescope Fine Guidance Sensor Astrometry of the Low-Mass Binary L722-22". The Astronomical Journal. 116 (3): 1440. Bibcode:1998AJ....116.1440H. doi:10.1086/300516. ISSN 1538-3881.
  11. ^ "Hubble instruments". sci.esa.int. Retrieved 2017-03-03.

Fine Guidance Sensor (HST)

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