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Rossi X-ray Timing Explorer

Rossi X-ray Timing Explorer
Artist impression of RXTE telescope
General information
NSSDC ID 1995-074A
Organization NASA
Major contractors MIT · GSFC
Launch date 30 December 1995 at 13:48:00 UTC
Launch site Cape Canaveral SLC-17A
Launch vehicle Delta II 7920
Mass 3,200 kilograms (7,100 lb)
Type of orbit circular orbit
Orbit height 600 km
Orbit period 92.5999984741211 minutes
All Sky Monitor (ASM) Energy range: 2-12 keV[1]
Proportional Counter Array (PCA) Energy range: 2-60 keV
High-Energy X-ray Timing Experiment (HEXTE) Energy range: 15-250 keV
Website RXTE home page
References: [2]
Excentricity 0.0
Orbital inclination 28.5°
Apoapsis 4,090 kilometres (2,540 mi)
Periapsis 4,090 kilometres (2,540 mi)
Power 800.0 watts
XTE launches

The Rossi X-ray Timing Explorer (RXTE) is a satellite that observed the time structure of astronomical X-ray sources, named after Bruno Rossi. The RXTE has three instruments—the Proportional Counter Array, the High-Energy X-ray Timing Experiment (HEXTE), and the All Sky Monitor. 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.[3] 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.[4] In April 2008, RXTE data was used to infer the size of the smallest known black hole.[5]

RXTE ceased science operations on 3 January 2012.[6]

NASA scientists said that the decommissioned RXTE would re-enter the Earth's atmosphere "between 2014 and 2023".[7]


  • Instruments 1
    • All-Sky Monitor (ASM) 1.1
    • Proportional Counter Array (PCA) 1.2
    • The High Energy X-ray Timing Experiment (HEXTE) 1.3
  • References 2
  • External links 3


All-Sky Monitor (ASM)

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:[8]

  • Energy range: 2-12 keV
  • Time resolution: 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)

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:[9]

  • 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)

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. Automatic gain control was provided by using a 241Am radioactive source mounted in each detector's field of view. The HEXTE's basic properties were:[10]

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

External links

  • MIT's Rossi X-Ray Timing Explorer Project
  • NASA Mission Site
  • Video documentary
  • Variations in the X-ray Sky by RXTE (1997)
  • RXTE Reveals the Cloudy Cores of Active Galaxies
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