Rossi X-ray Timing Explorer

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Rossi X-ray Timing Explorer
RXTE 3D Model
Artist impression of RXTE telescope
Names RXTE
Explorer 69
Mission type Astronomy
Operator NASA
COSPAR ID 1995-074A
SATCAT no. 23757
Website RXTE home page
Mission duration 16 years, 6 days
Spacecraft properties
Manufacturer GSFC
MIT (All-Sky Monitor)
Launch mass 3,200 kg (7,100 lb)
Power 800 W
Start of mission
Launch date 13:48, December 30, 1995 (1995-12-30T13:48)[1]
Rocket Delta II 7920
Launch site Cape Canaveral SLC-17A
End of mission
Disposal Decommissioned
Deactivated January 5, 2012 (2012-01-05)
Orbital parameters
Reference system Geocentric
Regime Low Earth
Semi-major axis 6,753 km (4,196 mi)
Eccentricity 0.0002672
Perigee 380.9 km (236.7 mi)
Apogee 384.5 km (238.9 mi)
Inclination 22.9842 degrees
Period 92.1 minutes
RAAN 221.8627 degrees
Argument of perigee 256.7652 degrees
Mean anomaly 103.2545 degrees
Mean motion 14.04728277 rev/day
Epoch 27 April 2016, 10:21:58 UTC[2]
Revolution no. 13218
Main telescope
Type Proportional counter
Scintillator (HEXTE)
Wavelengths 2–250 keV (X-ray)
ASM All Sky Monitor (2-12 keV)[3]
PCA Proportional Counter Array (2-60 keV)
HEXTE High-Energy X-ray Timing Experiment (15-250 keV)
← IMP-8

The Rossi X-ray Timing Explorer (RXTE) is a satellite that observed the time variation of astronomical X-ray sources, named after Bruno Rossi. The RXTE has three instruments—an All Sky Monitor, the Proportional Counter Array, and the High-Energy X-ray Timing Experiment (HEXTE). The RXTE observed X-rays from black holes, neutron stars, X-ray pulsars and X-ray bursts. It was funded as part of the Explorer program, and is sometimes also called Explorer 69.

RXTE was launched from Cape Canaveral on 30 December 1995 on a Delta rocket, has an International Designator of 1995-074A and a mass of 3200 kg.

Observations from the Rossi X-ray Timing Explorer have been used as evidence for the existence of the frame-dragging effect predicted by the theory of general relativity. RXTE results have, as of late 2007, been used in more than 1400 scientific papers.

In January 2006, it was announced that Rossi had been used to locate a candidate intermediate-mass black hole named M82 X-1.[4] In February 2006, data from RXTE was used to prove that the diffuse background X-ray glow in our galaxy comes from innumerable, previously undetected white dwarfs and from other stars' coronae.[5] In April 2008, RXTE data was used to infer the size of the smallest known black hole.[6]

RXTE ceased science operations on 3 January 2012.[7]

NASA scientists said that the decommissioned RXTE would re-enter the Earth's atmosphere "between 2014 and 2023".[8]


XTE launches

All-Sky Monitor (ASM)[edit]

The ASM consists of three wide-angle shadow cameras equipped with proportional counters with a total collecting area of 90 square cm. The instrumental properties were:[9]

  • Energy range: 2-12 keV
  • Time resolution: observes 80% of the sky every 90 minutes
  • Spatial resolution: 3' × 15'
  • Number of shadow cameras: 3, each with 6 × 90 degrees FOV
  • Collecting area: 90 cm2
  • Detector: Xenon proportional counter, position-sensitive
  • Sensitivity: 30 mCrab

It was built by the CSR at MIT. The principal investigator was Dr. Hale Bradt.

Proportional Counter Array (PCA)[edit]

The PCA is an array of five proportional counters with a total collecting area of 6500 square cm. The instrument was built by the EUD (formerly 'LHEA') at GSFC. The PCA principal investigator was Dr. Jean H. Swank.

The instrumental properties were:[10]

  • Energy range: 2-60 keV
  • Energy resolution: < 18% at 6 keV
  • Time resolution: 1 µs
  • Spatial resolution: collimator with 1 degree FWHM (Full Width at Half Maximum)
  • Detectors: 5 proportional counters
  • Collecting area: 6500 cm2
  • Layers: 1 propane veto; 3 xenon, each split into two; 1 xenon veto layer
  • Sensitivity: 0.1 mCrab
  • Background: 2 mCrab

The High Energy X-ray Timing Experiment (HEXTE)[edit]

The HEXTE consists of two clusters each containing four phoswich scintillation detectors. Each cluster could "rock" (beamswitch) along mutually orthogonal directions to provide background measurements 1.5 or 3.0 degrees away from the source every 16 to 128 s. In addition, the input was sampled at 8 microseconds so as to detect time varying phenomena. Automatic gain control was provided by using a 241
radioactive source mounted in each detector's field of view. The HEXTE's basic properties were:[11]

  • Energy range: 15-250 keV
  • Energy resolution: 15% at 60 keV
  • Time sampling: 8 microseconds
  • Field of view: 1 degree FWHM
  • Detectors: 2 clusters of 4 NaI/CsI scintillation counters
  • Collecting area: 2 × 800 cm2
  • Sensitivity: 1 Crab = 360 count/s per HEXTE cluster
  • Background: 50 count/s per HEXTE cluster

The HEXTE was designed and built by the Center for Astrophysics & Space Sciences (CASS) at the University of California, San Diego. The HEXTE principal investigator was Dr. Richard E. Rothschild.


  1. ^ "RXTE Mission". 2002-02-22. Retrieved 2012-02-03. 
  2. ^ "XTE Satellite details 1995-074A NORAD 23757". N2YO. 27 April 2016. Retrieved 27 April 2016. 
  3. ^ The RXTE All Sky Monitor Data Products
  4. ^ "Dying Star Reveals More Evidence for New Kind of Black Hole". Retrieved 2012-02-03. 
  5. ^ "Galactic Glow Gleaned". 
  6. ^ "NASA Scientists Identify Smallest Known Black Hole". 2008-04-01. 
  7. ^ "The RXTE Mission is Approaching the End of Science Operations". 2012-01-04. 
  8. ^ "NASA's ageing black hole-stalking probe switched off". 2012-01-11. 
  9. ^ "All-Sky Monitor (ASM)". 2002-02-04. Retrieved 2012-02-03. 
  10. ^ "Proportional Counter Array (PCA)". 2006-08-08. Retrieved 2012-02-03. 
  11. ^ "High Energy X-ray Timing Experiment (HEXTE)". 1999-09-14. Retrieved 2012-02-03. 

External links[edit]