Granat

This is a good article. Click here for more information.
Source: Wikipedia, the free encyclopedia.
For other uses, see Granat (disambiguation).
International Astrophysical Observatory "GRANAT"
picture credit: NASA
Mission typeGamma-ray astronomy
OperatorSoviet space program
COSPAR ID1989-096A Edit this at Wikidata
SATCAT no.20352
Websitehea.iki.rssi.ru/GRANAT/granat.html
Mission duration9 years
Spacecraft properties
NPO Lavochkin[1]
Launch mass~ 4,400 kg (9,700 lb)
Payload mass~ 2,300 kg (5,100 lb)
Dimensions4 m × 2.5 m (13.1 ft × 8.2 ft)
Power400 W
Start of mission
Launch date20:20:00, December 1, 1989 (UTC) (1989-12-01T20:20:00Z)
Proton-K Blok D-1[3]
Launch siteBaikonur Cosmodrome 200/40
End of mission
Disposaldeorbited
Last contact27 November 1998
Decay dateMay 25, 1999 (1999-05-25)[2]
Orbital parameters
Reference systemGeocentric[1]
RegimeHighly elliptical
Eccentricity0.92193
Perigee altitude1,760 kilometres (1,090 mi)[4]
Apogee altitude202,480 kilometres (125,820 mi)
Inclination51.9 degrees
Period5,880 minutes
Epoch01 December 1989
Main telescope
NameSIGMA
Type
MeV
)
Instruments
SIGMA X-ray/gamma-ray telescope[5]
ART-P X-ray telescope[6]
ART-S X-ray spectrometer[7]
PHEBUS Gamma-burst detector[8]
WATCH All-sky monitor[7]
KONUS GRB experiment[7]
TOURNESOL GRB experiment[7]
 

The International Astrophysical Observatory "GRANAT" (usually known as Granat;

Proton rocket and placed in a highly eccentric four-day orbit
, of which three were devoted to observations. It operated for almost nine years.

In September 1994, after nearly five years of directed observations, the gas supply for its

attitude control was exhausted and the observatory was placed in a non-directed survey mode. Transmissions finally ceased on 27 November 1998.[3]

With seven different instruments on board, Granat was designed to observe the universe at energies ranging from

keV
range. One instrument, WATCH, was designed to monitor the sky continuously and alert the other instruments to new or interesting X-Ray sources. The ART-S spectrometer covered the X-ray energy range while the KONUS-B and TOURNESOL experiments covered both the X-ray and gamma ray spectrum.

Spacecraft

Granat was a three-axis-stabilized spacecraft and the last of the

solar arrays. The power made available to the scientific instruments was approximately 400 W.[1]

Launch and orbit

Proton launch vehicle carrying Granat

The spacecraft was launched on 1 December 1989 aboard a

perigee of 202,480 km/1,760 km respectively and an inclination of 51.9 degrees.[4]
This meant that solar and lunar perturbations would significantly increase the orbits inclination while reducing its eccentricity, such that the orbit had become near-circular by the time Granat completed its directed observations in September 1994. (By 1991, the perigee had increased to 20,000 km; by September 1994, the apogee/perigee was 59,025 km / 144,550 km at an inclination of 86.7 degrees.)

Three days out of the four-day orbit were devoted to observations.

reentered the Earth's atmosphere on May 25, 1999.[2]

Granat observatory orbit change (1994 predictions)[4]
Date
Perigee
 (km)
Apogee
 (km)
Arg.perigee
(deg)
Inc.
 (deg)		 Long.asc.node (deg)
December 1, 1989 1,760 202,480 285 51.9 20.0
December 1, 1991 23,893 179,376 311.9 82.6 320.3
December 1, 1994 58,959 144,214 343.0 86.5 306.9
December 1, 1996 42,088.8 160,888 9.6 93.4 302.2

Instrumentation

SIGMA

SIGMA instrument

The hard X-ray and low-energy gamma-ray SIGMA

CEA (Saclay). It covered the energy range 35–1300 keV,[5] with an effective area of 800 cm2 and a maximum sensitivity field of view of ~5°×5°. The maximum angular resolution was 15 arcmin.[9] The energy resolution was 8% at 511 keV.[8] Its imaging capabilities were derived from the association of a coded mask and a position sensitive detector based on the Anger camera principle.[3]

ART-P

ART-P instrument

The ART-P X-ray telescope was the responsibility of the

Crab nebula source (= 1 "mCrab") in an eight-hour exposure. The maximum time resolution was 4 ms.[3][8]

ART-S

The ART-S X-ray spectrometer, also built by the IKI, covered the energy range 3 to 100 keV. Its field of view was 2° by 2°. The instrument consisted of four detectors based on spectroscopic MWPCs, making an effective area of 2,400 cm2 at 10 keV and 800 cm2 at 100 keV. The time resolution was 200 microseconds.[3]

PHEBUS

The PHEBUS experiment was designed by

CESR (Toulouse) to record high energy transient events in the range 100 keV to 100 MeV. It consisted of two independent detectors and their associated electronics. Each detector consisted of a bismuth germanate (BGO) crystal 78 mm in diameter by 120 mm thick, surrounded by a plastic anti-coincidence jacket. The two detectors were arranged on the spacecraft so as to observe 4π steradians. The burst mode was triggered when the count rate in the 0.1 to 1.5 MeV energy range exceeded the background level by 8 sigma in either 0.25 or 1.0 seconds. There were 116 energy channels.[3]

WATCH

Starting in January 1990, four WATCH instruments, designed by the Danish Space Research Institute, were in operation on the Granat observatory. The instruments could localize bright sources in the 6 to 180 keV range to within 0.5° using a Rotation Modulation Collimator. Taken together, the instruments' three fields of view covered approximately 75% of the sky. The energy resolution was 30% FWHM at 60 keV. During quiet periods, count rates in two energy bands (6 to 15 and 15 to 180 keV) were accumulated for 4, 8, or 16 seconds, depending on onboard computer memory availability. During a burst or transient event, count rates were accumulated with a time resolution of 1 second per 36 energy channels.[3]

KONUS-B

The KONUS-B instrument, designed by the

pulse height analyzers
(PHAs), of which the first eight were measured with 1/16 s time resolution and the remaining with variable time resolutions depending on the count rate. The range of resolutions covered 0.25 to 8 s.

The KONUS-B instrument operated from 11 December 1989 until 20 February 1990. Over that period, the "on" time for the experiment was 27 days. Some 60 solar flares and 19 cosmic gamma-ray bursts were detected.[3]

TOURNESOL

The French TOURNESOL instrument consisted of four proportional counters and two optical detectors. The proportional counters detected photons between 2 keV and 20 MeV in a 6° by 6° field of view. The visible detectors had a field of view of 5° by 5°. The instrument was designed to look for optical counterparts of high-energy burst sources, as well as performing spectral analysis of the high-energy events.[3]

Science results

Over the initial four years of directed observations, Granat observed many galactic and extra-galactic X-ray sources with emphasis on the deep imaging and spectroscopy of the Galactic Center, broad-band observations of black hole candidates, and X-ray novae. After 1994, the observatory was switched to survey mode and carried out a sensitive all-sky survey in the 40 to 200 keV energy band.

Some of the highlights included:

Impact of the dissolution of the Soviet Union

After the end of the

dish antenna. With the breakup of the Union, the Crimea region found itself part of the newly independent Ukraine and the center was put under Ukrainian national control, prompting new political hurdles.[1]

The main and most urgent problem, however, was in finding funds to support the continued operation of the spacecraft amid the spending crunch in post-Soviet Russia. The French space agency, having already contributed significantly to the project (both scientifically and financially), took upon itself to fund the continuing operations directly.[1]

See also

References

Public Domain This article incorporates public domain material from websites or documents of the

National Aeronautics and Space Administration
.

  1. ^ a b c d e "Granat X-ray and Gamma-ray Observatory". The Federation of American Scientists. Archived from the original on 2007-02-06. Retrieved 2007-12-06.
  2. ^ a b c "1999 Reentries" (PDF). The Aerospace Corporation, Center for Orbital and Reentry Debris Studies. Archived from the original (PDF) on 2005-01-22. Retrieved 2007-12-06.
  3. ^ a b c d e f g h i "GRANAT". NASA HEASARC. Retrieved 2007-12-05.
  4. ^
    NPO Lavochkin, Orbital Astrophysical Observatory "Granat": Problems of Control Archived 2007-10-31 at the Wayback Machine
    , Zemlya i Vselennaya, 1994, no. 2. Only four rows from a table of twenty used here.
  5. ^
    A&A Supplement Series
    , 1993, no. 97.
  6. ^ a b Molkov, S.V., Grebenev, S.A., Pavlinsky, M.N., Sunyaev. "GRANAT/ART-P OBSERVATIONS OF GX3+1: TYPE I X-RAY BURST AND PERSISTENT EMISSION", Mar 1999. 4pp. arXiv e-Print (astro-ph/9903089v1).
  7. ^ a b c d e f "The Granat Satellite". NASA HEASARC Imagine the Universe!. Archived from the original on 2014-05-14. Retrieved 2007-12-05.
  8. ^
    IKI RAN
    . Retrieved 2007-12-05.
  9. ^ a b M.G. Revnivtsev, R.A. Sunyaev, M.R. Gilfanov, E.M. Churazov, A. Goldwurm, J. Paul, P. Mandrou and J. P. Roques "A hard X-ray sky survey with the SIGMA telescope of the GRANAT observatory", (2004) Astronomy Letters, vol. 30, p.527-533
  10. IKI RAN
    . Retrieved 2008-05-25.

External links

Retrieved from "https://en.wikipedia.org/w/index.php?title=Granat&oldid=1174014604"
This page is based on the copyrighted Wikipedia article: Granat. Articles is available under the CC BY-SA 3.0 license; additional terms may apply.Privacy Policy