Herschel Space Observatory: Wikis

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Herschel Space Observatory
Graphic of Herschel Space Observatory
General information
NSSDC ID 2009-026A
Organization European Space Agency (ESA) with Thales Alenia Space as Prime contractor
Launch date 14 May 2009 13:12:02 UTC
Launched from Guiana Space Centre
French Guiana
Launch vehicle Ariane 5 ECA
Mission length elapsed: 8 months and 1 day
Mass 3,300 kg (7,300 lb)
Type of orbit Lissajous orbit
Orbit height 1,500,000 km (930,000 mi)
Orbit period 1 year
Orbit velocity 7,500 m/s (27,000 km/h)
Location Lagrangian point L2
Telescope style Ritchey-Chrétien
Wavelength 60-670 µm (far-infrared)
Diameter 3,500 mm (140 in), f/0.5
Collecting area 9.6 m2 (103 sq ft)
Focal length 28.5 m (94 ft), f/8.7
Instruments
HIFI Heterodyne Instrument for the Far Infrared
PACS Photodetector Array Camera and Spectrometer
SPIRE Spectral and Photometric Imaging Receiver
Website herschel.esac.esa.int

The Herschel Space Observatory is a space observatory from the European Space Agency (ESA). It was originally proposed in 1982 by a consortium of European scientists. The mission is named jointly after Sir William Herschel, the discoverer of the infrared spectrum and planet Uranus, and his sister and observing partner Caroline.[1]

Herschel can see the coldest and dustiest objects in space; for example, cool cocoons where stars form and dusty galaxies just starting to bulk up with new stars. The observatory will sift through star-forming clouds -- the "slow cookers" of star ingredients -- to trace the path by which potentially life-forming molecules, such as water, form.

The US space agency NASA played a key role in the development of two of the mission's three instruments, and will make important contributions to data and science analyses. NASA's Jet Propulsion Laboratory in Pasadena, Calif., developed and built the "spider web" bolometers for Herschel's spectral and photometric imaging receiver (SPIRE) instrument, which are 40 times more sensitive than previous versions. It also developed and built mixers, local oscillator chains and power amplifiers for the heterodyne instrument for the far infrared (HIFI).[2]

Contents

Science

Herschel will specialise in collecting light from objects in our Solar System as well as the Milky Way and even extragalactic objects billions of light-years away, such as newborn galaxies, and is charged with four primary areas of investigation:[3]

Instrumentation

The mission, formerly titled the Far Infrared and Sub-millimetre Telescope (FIRST), involves the first space observatory to cover the full far infrared and submillimetre waveband.[3] At 3.5 meters wide, its telescope incorporates the largest mirror ever deployed in space.[4] The light is focused onto three instruments with detectors kept at temperatures below 2 K (−271 °C). The instruments are cooled with liquid helium, boiling away in a near vacuum at a temperature of approximately 1.4 K (−272 °C). The 2,000-litre supply of helium on board the spacecraft will limit its operational lifetime, nonetheless it is expected to be operational for at least 3 years.[5]

Herschel carries three detectors:[6]

PACS (Photodetecting Array Camera and Spectrometer)
An imaging camera and low-resolution spectrometer covering wavelengths from 55 to 210 micrometres. The spectrometer has a spectral resolution between R=1000 and R=5000 and is able to detect signals as weak as −63dB. It operates as an integral field spectrograph, combining spatial and spectral resolution. The imaging camera can image simultaneously in two bands (either 60–85/85–130 micrometres and 130–210 micrometres) with a detection limit of a few millijanskys.[7][8]
Herschel in a clean room
SPIRE (Spectral and Photometric Imaging Receiver)
An imaging camera and low-resolution spectrometer covering 194 to 672 micrometre wavelength. The spectrometer has a resolution between R=40 and R=1000 at a wavelength of 250 micrometres and is able to image point sources with brightnesses around 100 millijanskys (mJy) and extended sources with brightnesses of around 500 mJy.[9] The imaging camera has three bands, centered at 250, 350 and 500 micrometres, each with 139, 88 and 43 pixels respectively. It should be able to detect point sources with brightness above 2 mJy and between 4 and 9 mJy for extended sources. A prototype of the SPIRE imaging camera flew on the BLAST high-altitude balloon.
HIFI (Heterodyne Instrument for the Far Infrared)
A heterodyne detector which is able to electronically separate radiation of different wavelengths, giving a spectral resolution as high as R=107.[10] The spectrometer can be operated within two wavelength bands, from 157 to 212 micrometres and from 240 to 625 micrometres.

Service module

A common service module (SVM) was designed and built by Thales Alenia Space in its Turin plant, for the Herschel and Planck missions combined into one single program.[11]

Structurally, the Herschel and Planck SVM's are very similar. Both SVM's are of octagonal shape and for both, each panel is dedicated to accommodate a designated set of warm units, while taking into account the dissipation requirements of the different warm units, of the instruments as well as the spacecraft.

Furthermore, on both spacecraft a common design for the avionics, the attitude control and measurement system (ACMS) and the command and data management system (CDMS), and power subsystem and the tracking, telemetry and command subsystem (TT&C) has been achieved.

All spacecraft units on the SVM are redundant.

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Power subsystem

On each spacecraft, the power subsystem consists of the solar array, employing triple-junction solar cells, a battery and the power control unit (PCU). It is designed to interface with the 30 sections of each solar array, provide a regulated 28 V bus, distribute this power via protected outputs and to handle the battery charging and discharging.

For Herschel, the solar array is fixed on the bottom part of the baffle designed to protect the cryostat from the sun. The three-axis attitude control system maintains this baffle in direction of the sun. The top part of this baffle is covered with Optical solar reflector (OSR) mirrors reflecting 98% of the sun energy, avoiding heating of the cryostat.

Attitude and orbit control

This function is performed by the attitude control computer (ACC) which is the platform for the ACMS. It is designed to fulfil the pointing and slewing requirements of the Herschel and Planck payload.

The Herschel spacecraft is three-axis stabilized, the absolute pointing error needs to be less than 3.7 arc sec.

The main sensor of the line of sight in both spacecraft is the star tracker.

Launch and orbit

The spacecraft, built in the Cannes Mandelieu Space Center, under Thales Alenia Space Contractorship, was successfully launched from the Guiana Space Centre in French Guiana at 13:12:02 UTC on 14 May 2009, aboard an Ariane 5 rocket, along with the Planck spacecraft, and placed on a very elliptical orbit (perigee: 270.0 km (intended 270.0±4.5), apogee: 1,197,080 km (intended 1,193,622±151,800), inclination 5.99 deg (intended 6.00±0.06)[12]), on its way towards the second Lagrangian point.[13][14][15]

On June 14, 2009, ESA successfully sent the command for the cryocover to open which will allow the PACS system to see the sky and transmit images in a few weeks. The lid had to remain closed until the telescope was well into space to prevent contamination. Herschel is reported to have completed 90% of the distance to its orbit 1.5 million km away from Earth.[16]

Five days later the first set of test photos, depicting M51 Group, was published by ESA.[17]

In mid-July 2009, approximately sixty days after launch, it entered a Lissajous orbit of 800,000 km average radius around the second Lagrangian point (L2) of the Earth-Sun system, 1.5 million kilometres from the Earth.[1][15]

Operational mission

On 21 July 2009, Herschel commissioning was declared successful, allowing the start of the operational phase. A formal handover of the overall responsibility of Herschel was declared from the programme manager Thomas Passvogel to the mission manager Johannes Riedinger.[15]

See also

References

  1. ^ a b "Herschel Factsheet". European Space Agency. 17 April 2009. http://www.esa.int/esaSC/SEMA539YFDD_index_0.html. Retrieved 2009-05-12.  
  2. ^ "Herschel: Exploring the Birth of Stars and Galaxies". NASA. http://www.nasa.gov/mission_pages/herschel/overview.html.  
  3. ^ a b "Herschel". European Space Agency Science & Technology. http://sci.esa.int/science-e/www/area/index.cfm?fareaid=16. Retrieved 2007-09-29.  
  4. ^ "Herschel Space Observatory". Imperial College. http://astro.imperial.ac.uk/Research/Infrared/Herschel/. Retrieved 2007-09-29.  
  5. ^ Jonathan Amos (9 February 2009). "'Silver Sensation' Seeks Cold Cosmos". BBC News. http://news.bbc.co.uk/2/hi/science/nature/7864087.stm. Retrieved 2009-03-06.  
  6. ^ "Herschel: Science payload". European Space Agency. 20 November 2008. http://www.esa.int/esaSC/120390_index_0_m.html. Retrieved 2009-03-07.  
  7. ^ "PACS – Photodetector Array Camera and Spectrometer". http://herschel.esac.esa.int/Docs/Flyers/PACS_flyer_4July2007.pdf. Retrieved 2007-09-29.  
  8. ^ "The Photodetector Array Camera and Spectrometer (PACS) for the Herschel Space Observatory". http://herschel.esac.esa.int/Publ/2008/SPIE2008_PACS_paper.pdf. Retrieved 2009-08-19.  
  9. ^ "SPIRE – Spectral and Photometric Imaging Receiver". European Space Agency. http://herschel.esac.esa.int/Docs/Flyers/SPIRE_flyer_4July2007.pdf. Retrieved 2007-09-29.  
  10. ^ "HIFI – Heterodyne Instrument for the Far Infrared". European Space Agency. http://herschel.esac.esa.int/Docs/Flyers/HIFI_flyer_4July2007.pdf. Retrieved 2007-09-29.  
  11. ^ Planck Science Team (2005) (.PDF). Planck: The Scientific Programme (Blue Book). ESA-SCI (2005)-1. Version 2. European Space Agency. http://www.rssd.esa.int/SA/PLANCK/docs/Bluebook-ESA-SCI%282005%291_V2.pdf. Retrieved 2009-03-06.  
  12. ^ Herschel Science Centre Operations (B)Log. European Space Agency. 14 May 2009. Retrieved on 2009-05-18
  13. ^ Leo Cendrowicz (14 May 2009). "Two Telescopes to Measure the Big Bang". Time. http://www.time.com/time/health/article/0,8599,1898174,00.html. Retrieved 2009-05-16.  
  14. ^ (.SWF) Launch of Herschel and Planck satellites. [video]. Arianespace. 14 May 2009. http://www.videocorner.tv/videocorner2/live_flv/index.php?langue=en. Retrieved 2009-05-16.  
  15. ^ a b c Herschel Latest News, on line herschel.esac.esa.int
  16. ^ Amos, Jonathan (June 14, 2009). "Herschel telescope 'opens eyes'". BBC News. http://news.bbc.co.uk/2/hi/science/nature/8099105.stm. Retrieved June 14, 2009.  
  17. ^ "Herschel's 'sneak preview': a glimpse of things to come". ESA. 2009-06-19. http://herschel.esac.esa.int/SneakPreview.shtml. Retrieved 2009-06-19.  

Further reading

External links


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