Rossi X-ray Timing Explorer

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.

• Required continuous TDRSS Multiple Access (MA) return link coverage except for zone of exclusion: Real-time and playback of engineering/housekeeping data at 16 or 32 kbs - Playback of science data at 48 or 64 kbs.{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTelemetry.action?id=1995-074A |title=Telecommunications Description |publisher=NASA |date=28 October 2021 |access-date=28 November 2021}} {{PD-notice}}
• Requires 20 minutes of SSA contacts with alternating TDRSS per orbit: Real-time and playback of engineering/housekeeping data at 32 kbs - Playback of science data at 512 or 1024 kbs.
• For launch and contingency, required TDRSS MA/SSA real-time engineering and housekeeping at 1 kbs.
• The bit error rate shall be less than 1 in 10E8 for at least 95% of the orbits.

File:XTE launch.gif

File:RXTE preparations.jpg

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.{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1995-074A-01 |title=Experiment: All-Sky Monitor (ASM) |publisher=NASA |date=28 October 2021 |access-date=28 November 2021}} {{PD-notice}} The ASM consisted of three wide-angle shadow cameras equipped with proportional counters with a total collecting area of {{cvt|90|cm2}}. The instrumental properties were:{{cite web |url=http://heasarc.gsfc.nasa.gov/docs/xte/ASM.html |title=All-Sky Monitor (ASM) |publisher=Heasarc.gsfc.nasa.gov |date=2002-02-04 |access-date=2012-02-03}} {{PD-notice}}{{cite web |url=https://heasarc.gsfc.nasa.gov/docs/xte/asm_products_guide.html |title=The RXTE All Sky Monitor Data Products |publisher=NASA |date=26 August 1997 |access-date=28 November 2021}} {{PD-notice}}

• 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° FoV;
• Collecting area: {{cvt|90|cm2}};
• Detector: Xenon proportional counter, position-sensitive;
• Sensitivity: 30 mCrab.

It was built by the CSR at Massachusetts Institute of Technology. The principal investigator was [http://web.mit.edu/physics/people/faculty/bradt_hale.html 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.{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1995-074A-03 |title=Experiment: High Energy X-ray Timing Experiment (HEXTE) |publisher=NASA |date=28 October 2021 |access-date=28 November 2021}} {{PD-notice}} 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 {{SimpleNuclide|americium|241|link=yes}} radioactive source mounted in each detector's field of view. The HEXTE's basic properties were:{{cite web |url=http://heasarc.gsfc.nasa.gov/docs/xte/HEXTE.html |title=High Energy X-ray Timing Experiment (HEXTE) |publisher=NASA |date=1999-09-14 |access-date=2012-02-03}} {{PD-notice}}

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

The HEXTE was designed and built by the [http://cass.ucsd.edu Center for Astrophysics & Space Sciences (CASS)] at the University of California, San Diego. The HEXTE principal investigator was [https://web.archive.org/web/20081229041202/http://mamacass.ucsd.edu/people/rrothschild.html Dr. Richard E. Rothschild].

The Proportional Counter Array (PCA) provides approximately {{cvt|6500|cm2}} 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.{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1995-074A-02 |title=Experiment: Proportional Counter Array (PCA) |publisher=NASA |date=28 October 2021 |access-date=28 November 2021}} {{PD-notice}} The PCA was an array of five proportional counters with a total collecting area of {{cvt|6500|cm2}}. The instrumental properties were:{{cite web |url=https://heasarc.gsfc.nasa.gov/docs/xte/learning_center/pca.html |title=Proportional Counter Array (PCA) |publisher=NASA |date=2011-12-06 |access-date=2018-10-05}}

• Energy range: 2–60 keV;
• Energy resolution: <18% at 6 keV;
• Time resolution: 1 μs
• Spatial resolution: collimator with 1° (FWHM);
• Detectors: 5 proportional counters;
• Collecting area: {{cvt|6500|cm2}};
• Layers: 1 propane veto; 3 Xenon, each split into two; 1 Xenon veto layer;
• Sensitivity: 0.1-mCrab;
• Background: 90-mCrab.

The PCA is being built by the Laboratory for High Energy Astrophysics (LHEA) at Goddard Space Flight Center. The principal investigator was Jean Swank.

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.{{cite news |url=http://www.scienceblog.com/cms/dying_star_reveals_more_evidence_for_new_kind_of_black_hole_9685 |title=Dying Star Reveals More Evidence for New Kind of Black Hole |newspaper=Scienceblog.com |date=8 January 2006 |publisher=Science Blog |access-date=2012-02-03 |last1=Com |first1=Scienceblog}} 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.{{cite web |url=http://skyandtelescope.com/news/article_1681_1.asp |title=Galactic Glow Gleaned}} In April 2008, RXTE data was used to infer the size of the smallest known black hole.{{cite web |title=NASA Scientists Identify Smallest Known Black Hole |url=http://www.nasa.gov/centers/goddard/news/topstory/2008/smallest_blackhole.html |date=2008-04-01}} {{PD-notice}}

RXTE ceased science operations on 12 January 2012.{{cite web |title=The RXTE Mission is Approaching the End of Science Operations |url=http://heasarc.nasa.gov/docs/xte/xhp_new.html#endofoperations |archive-url=https://web.archive.org/web/20040107162230/http://heasarc.nasa.gov/docs/xte/xhp_new.html#endofoperations |url-status=dead |archive-date=2004-01-07 |date=2012-01-04}} {{PD-notice}}

NASA scientists said that the decommissioned RXTE would re-enter the Earth's atmosphere "between 2014 and 2023" (30 April 2018).{{cite web |url=https://www.theregister.co.uk/2012/01/11/rxte_satellite/ |title=NASA's aging black hole-stalking probe switched off |website=theregister.co.uk |date=11 January 2012 |access-date=28 November 2021}} Later, it became clear that the satellite would re-enter in late April or early May 2018,{{cite web |title=NASA Frequently Asked Questions: RXTE Spacecraft Re-entry |url=https://www.nasa.gov/feature/goddard/2018/nasa-frequently-asked-questions-rxte-spacecraft-re-entry |publisher=NASA |date=25 April 2018 |access-date=28 November 2021}} and the spacecraft fell out of orbit on 30 April 2018.{{cite web |url=https://www.space.com/40592-nasa-rxte-satellite-falls-to-earth.html |title=A Pioneering NASA Satellite Just Fell to Earth After 2 Decades in Space |publisher=Space.com |date=15 May 2018 |access-date=28 November 2021}}

{{Portal|Spaceflight}}

• List of X-ray space telescopes
• Neutron Star Interior Composition Explorer (NICER, launched in June 2017 and attached to ISS)

{{Reflist|30em}}

{{Commons category|RXTE}}

• [http://xte.mit.edu/ MIT's Rossi X-Ray Timing Explorer Project]
• [http://heasarc.gsfc.nasa.gov/docs/xte/xte_1st.html NASA RXTE Mission Site]
• [https://web.archive.org/web/20060102023814/http://www.ucsd.tv/search-details.asp?showID=1713 Video documentary]
• [https://web.archive.org/web/20061001024105/http://heasarc.nasa.gov/docs/objects/heapow/archive/transients/asm_movie.html Variations in the X-ray Sky by RXTE (1997)]
• [http://www.nasa.gov/content/goddard/rxte-reveals-the-cloudy-cores-of-active-galaxies/ RXTE Reveals the Cloudy Cores of Active Galaxies]

{{Explorer program}}

{{Orbital launches in 1995}}

{{Space observatories}}

Category:Spacecraft launched in 1995

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Category:X-ray telescopes