Rossi X-ray Timing Explorer


Rossi X-ray Timing Explorer
RXTE 3D Model
Artist impression of RXTE telescope
Explorer 69
Mission typeAstronomy
COSPAR ID1995-074A
SATCAT no.23757
WebsiteRXTE home page
Mission duration16 years, 6 days
Spacecraft properties
MIT (All-Sky Monitor)
Launch mass3,200 kg (7,100 lb)
Power800 W
Start of mission
Launch date13:48, December 30, 1995 (UTC) (1995-12-30T13:48Z)[1]
RocketDelta II 7920
Launch siteCape Canaveral SLC-17A
End of mission
DeactivatedJanuary 5, 2012 (2012-01-05)
Decay dateApril 30, 2018[2]
Orbital parameters
Reference systemGeocentric
RegimeLow Earth
Semi-major axis6,753 km (4,196 mi)
Perigee altitude380.9 km (236.7 mi)
Apogee altitude384.5 km (238.9 mi)
Inclination22.9842 degrees
Period92.1 minutes
RAAN221.8627 degrees
Argument of perigee256.7652 degrees
Mean anomaly103.2545 degrees
Mean motion14.04728277 rev/day
Epoch27 April 2016, 10:21:58 UTC[3]
Revolution no.13218
Main telescope
TypeProportional counter
Scintillator (HEXTE)
Wavelengths2–250 keV (X-ray)
ASM All Sky Monitor (2–12 keV)[4]
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) was a satellite that observed the time variation of astronomical X-ray sources, named after physicist Bruno Rossi. The RXTE had 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 had a mass of 3200 kg and was launched from Cape Canaveral on 30 December 1995 on a Delta rocket. Its International Designator is 1995-074A.


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.[5] 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.[6] In April 2008, RXTE data was used to infer the size of the smallest known black hole.[7]

RXTE ceased science operations on 3 January 2012.[8]

NASA scientists said that the decommissioned RXTE would re-enter the Earth's atmosphere "between 2014 and 2023".[9] Later it became clear that the satellite would re-enter in late April or early May 2018,[10] and the spacecraft fell out of orbit on April 30, 2018.[11]


XTE launches

All-Sky Monitor (ASM)

The ASM consisted of three wide-angle shadow cameras equipped with proportional counters with a total collecting area of 90 square cm. The instrumental properties were:[12]

  • 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)

The PCA was 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:[13]

  • 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: 90 mCrab

The High Energy X-ray Timing Experiment (HEXTE)

The HEXTE consisted 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:[14]

  • 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.

See also


  1. ^ "RXTE Mission". 2002-02-22. Retrieved 2012-02-03.
  2. ^ Reddy, Francis. "NASA's Rossi X-ray Timing Explorer Leaves Scientific 'Treasure Trove'". NASA. Retrieved 3 May 2018.
  3. ^ "XTE Satellite details 1995-074A NORAD 23757". N2YO. 27 April 2016. Retrieved 27 April 2016.
  4. ^ The RXTE All Sky Monitor Data Products
  5. ^ "Dying Star Reveals More Evidence for New Kind of Black Hole". Retrieved 2012-02-03.
  6. ^ "Galactic Glow Gleaned".
  7. ^ "NASA Scientists Identify Smallest Known Black Hole". 2008-04-01.
  8. ^ "The RXTE Mission is Approaching the End of Science Operations". 2012-01-04. Archived from the original on 2004-01-07.
  9. ^ "NASA's ageing black hole-stalking probe switched off". 2012-01-11.
  10. ^ "NASA FAQ: RXTE Spacecraft Re-entry". NASA. Retrieved 30 April 2018.
  11. ^ "A Pioneering NASA Satellite Just Fell to Earth After 2 Decades in Space". Retrieved 2018-05-15.
  12. ^ "All-Sky Monitor (ASM)". 2002-02-04. Retrieved 2012-02-03.
  13. ^ "About RXTE The PCA". 2011-12-06. Retrieved 2018-10-05.
  14. ^ "High Energy X-ray Timing Experiment (HEXTE)". 1999-09-14. Retrieved 2012-02-03.
RXTE preparations in 1995

External links

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