Astronomy:Fine Guidance Sensor (HST)

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Short description: Hubble Space Telescope instrument system
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The FGS were originally made by the optics company Perkin-Elmer, and as removable and repairable instruments it has been possible to refurbish them over the lifetime of the telescope.[8]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]

Observations

The smallest Kuiper Belt Object (KBO) yet detected at that time was discovered in 2009 by poring over data from the Hubble Space Telescope's fine guidance sensors.[12] They detected a transit of an object against a distant star, which, based on the duration and amount of dimming, was calculated to be a KBO about 1,000 meters (3,200 ft) in diameter.[12] It has been suggested that the Kepler observatory may be able to detect objects in the Oort cloud by their occultation of background stars,[13] and the Whipple proposal would also try to use this concept.

A Hubble FGS has also been used for astrometry, tracking the movement of different stars.[14] This ability was used for exoplanet research, where the motion of the star caused by the movement of planets around it was detected.[14] Hubble was used via the FGS sensors to detect the motion of star caused by an exoplanet orbiting it.[15] The effect on the red dwarf Gliese 876's by companion Gliese 876b was measured.[15]

FGS was used to study Double-star systems (aka Binary star systems) and to measure distances to astronomical bodies.[15]

FGS has also been used to observe asteroids and calculate their size.[16] Asteroids studied include (63) Ausonia, (15) Eunomia, (43) Ariadne, (44) Nysa, and (624) Hektor.[16]

See also

References

  1. ↑ "Hubble Space Telescope Systems". p. 20. https://asd.gsfc.nasa.gov/archive/sm3a/downloads/sm3a_media_guide/HST-systems.pdf. 
  2. ↑ 2.0 2.1 "Hubble's Instruments: FGS - Fine Guidance Sensors" (in en). https://www.spacetelescope.org/about/general/instruments/fgs/. 
  3. ↑ "NASA - Refurbished Fine Guidance Sensor (FGS)" (in en). https://www.nasa.gov/mission_pages/hubble/servicing/SM4/multimedia/FGS_practice_mm.html. 
  4. ↑ Fine Guidance Sensors Aboard the Hubble Space Telescope, the Scientific Capabilities of these Interferometer
  5. ↑ 5.0 5.1 5.2 "Fine Guidance Sensors" (in en). https://www.stsci.edu/home/hst/instrumentation/fgs. 
  6. ↑ 6.0 6.1 "NASA - Hubble Space Telescope Servicing Mission 4
    Fine Guidance Sensor"     (in en). https://www.nasa.gov/mission_pages/hubble/servicing/SM4/main/FGS_FS_HTML.html.     
  7. ↑ "Fine guidance sensors: Hubble's unsung heros". NewsTimes. http://www.newstimes.com/news/article/Fine-guidance-sensors-Hubble-s-unsung-heros-454038.php. 
  8. ↑ 8.0 8.1 "Fine guidance sensors: Hubble's unsung heros". NewsTimes. http://www.newstimes.com/news/article/Fine-guidance-sensors-Hubble-s-unsung-heros-454038.php. 
  9. ↑ 9.0 9.1 "Photo Index 1". https://spaceflight.nasa.gov/gallery/images/shuttle/sts-125/html/s125e009890.html. 
  10. ↑ 10.0 10.1 Hershey, John L.; Taff, L. G. (1998-01-01). "Hubble Space Telescope Fine Guidance Sensor Astrometry of the Low-Mass Binary L722-22" (in en). The Astronomical Journal 116 (3): 1440. doi:10.1086/300516. ISSN 1538-3881. Bibcode: 1998AJ....116.1440H. 
  11. ↑ "Hubble instruments" (in en-GB). http://sci.esa.int/hubble/34007-hubble-instruments/?fbodylongid=1461. 
  12. ↑ 12.0 12.1 "HubbleSite - NewsCenter - Hubble Finds Smallest Kuiper Belt Object Ever Seen (12/16/2009) - the Full Story". http://hubblesite.org/newscenter/archive/releases/2009/2009/33/full/. 
  13. ↑ DETECTABILITY OF OORT CLOUD OBJECTS USING KEPLER - 2009
  14. ↑ 14.0 14.1 ""Out of Whack" Planetary System Offers Clues to a Disturbing Past" (in en). UT News | The University of Texas at Austin. 2010-05-24. https://news.utexas.edu/2010/05/24/mcdonald_planetary_system. 
  15. ↑ 15.0 15.1 15.2 "Hubble Space Telescope – Fine Guidance Sensors". 27 January 2017. https://www.nasa.gov/content/hubble-space-telescope-fine-guidance-sensors. 
  16. ↑ 16.0 16.1 Tanga, P.; Hestroffer, D.; Cellino, A.; Lattanzi, M.; Martino, M. Di; Zappalà, V. (2003-04-01). "Asteroid observations with the Hubble Space Telescope FGS" (in en). Astronomy & Astrophysics 401 (2): 733–741. doi:10.1051/0004-6361:20030032. ISSN 0004-6361. Bibcode: 2003A&A...401..733T. 

External links



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