| Rossi X-ray Timing Explorer | |
| Names List: | Explorer 69 RXTE XTE |
| Image Alt: | RXTE 3D Model |
| Mission Type: | Astronomy |
| Operator: | NASA |
| Cospar Id: | 1995-074A |
| Satcat: | 23757 |
| Website: | RXTE home page |
| Mission Duration: | 16 years (achieved) |
| Spacecraft: | Explorer LXVIX |
| Spacecraft Type: | Rossi X-ray Timing Explorer |
| Spacecraft Bus: | X-ray Timing Explorer |
| Manufacturer: | Goddard Space Flight Center |
| Power: | 800 watts |
| Launch Date: | 30 December 1995, 13:48:00 UTC |
| Launch Rocket: | Delta II 7920-10 (Delta 230) |
| Launch Site: | Cape Canaveral, SLC-17A |
| Launch Contractor: | McDonnell Douglas Astronautics Company |
| Entered Service: | 30 December 1995 |
| Deactivated: | 12 January 2012 |
| Decay Date: | 30 April 2018 [1] |
| Orbit Reference: | Geocentric orbit[2] |
| Orbit Regime: | Low Earth orbit |
| Orbit Inclination: | 28.50° |
| Orbit Period: | 92.60 minutes |
| Apsis: | gee |
| Programme: | Explorer program |
| Previous Mission: | Solar Anomalous and Magnetospheric Particle Explorer (Explorer 68) |
| Next Mission: | Fast Auroral SnapshoT Explorer (Explorer 70) |
The Rossi X-ray Timing Explorer (RXTE) was a NASA 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 High-Energy X-ray Timing Experiment (HEXTE) and the Proportional Counter Array. 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 was also called Explorer 69.
RXTE had a mass of and was launched from Cape Canaveral on 30 December 1995, at 13:48:00 UTC, on a Delta II launch vehicle. Its International Designator is 1995-074A.[3]
The X-Ray Timing Explorer (XTE) mission has the primary objective to study the temporal and broad-band spectral phenomena associated with stellar and galactic systems containing compact objects in the energy range 2--200 KeV and in time scales from microseconds to years. The scientific instruments consists of two pointed instruments, the Proportional Counter Array (PCA) and the High-Energy X-ray Timing Experiment (HEXTE), and the All Sky Monitor (ASM), which scans over 70% of the sky each orbit. All of the XTE observing time were available to the international scientific community through a peer review of submitted proposals. XTE used a new spacecraft design that allows flexible operations through rapid pointing, high data rates, and nearly continuous receipt of data at the Science Operations Center (SOC) at Goddard Space Flight Center via a Multiple Access link to the Tracking and Data Relay Satellite System (TDRSS). XTE was highly maneuverable with a slew rate of greater than 6° per minute. The PCA/HEXTE could be pointed anywhere in the sky to an accuracy of less than 0.1°, with an aspect knowledge of around 1 arcminute. Rotatable solar panels enable anti-sunward pointing to coordinate with ground-based night-time observations. Two pointable high-gain antennas maintain nearly continuous communication with the TDRSS. This, together with 1 GB (approximately four orbits) of on-board solid-state data storage, give added flexibility in scheduling observations.[3]
The All-Sky Monitor (ASM) provided all-sky X-ray coverage, to a sensitivity of a few percent of the Crab Nebula intensity in one day, in order to provide both flare alarms and long-term intensity records of celestial X-ray sources.[5] The ASM consisted of three wide-angle shadow cameras equipped with proportional counters with a total collecting area of . The instrumental properties were:[6] [7]
It was built by the CSR at Massachusetts Institute of Technology. The principal investigator was Dr. Hale Bradt.
The High-Energy X-ray Timing Experiment (HEXTE) is a scintillator array for the study of temporal and temporal/spectral effects of the hard X-ray (20 to 200 keV) emission from galactic and extragalactic sources.[8] The HEXTE consisted of two clusters each containing four phoswich scintillation detectors. Each cluster could "rock" (beam switch) along mutually orthogonal directions to provide background measurements 1.5° or 3.0° away from the source every 16 to 128 seconds. In addition, the input was sampled at 8 microseconds so as to detect time-varying phenomena. Automatic gain control was provided by using an radioactive source mounted in each detector's field of view. The HEXTE's basic properties were:[9]
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.
The Proportional Counter Array (PCA) provides approximately of X-ray detector area, in the energy range 2 to 60 keV, for the study of temporal/spectral effects in the X-ray emission from galactic and extragalactic sources.[10] The PCA was an array of five proportional counters with a total collecting area of . The instrumental properties were:[11]
The PCA is being built by the Laboratory for High Energy Astrophysics (LHEA) at Goddard Space Flight Center. The principal investigator was Jean Swank.[11]
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 of Einstein. 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.[12] 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.[13] In April 2008, RXTE data was used to infer the size of the smallest known black hole.[14]
RXTE ceased science operations on 12 January 2012.[15]
NASA scientists said that the decommissioned RXTE would re-enter the Earth's atmosphere "between 2014 and 2023" (30 April 2018).[16] Later, it became clear that the satellite would re-enter in late April or early May 2018,[17] and the spacecraft fell out of orbit on 30 April 2018.[18]