Misplaced Pages

#936063

47-408: Gamma rays are too energetic to be focused with mirrors. The rays penetrate mirror materials instead of reflecting. Because gamma rays cannot be focused into an image in the traditional sense, a unique location for a gamma ray source cannot be determined as it is done with less energetic light. In addition, gamma ray bursts are brief flashes (often as little as 0.2 seconds) that occur randomly across

94-571: A general sky direction for bursts, which in many cases could augment the IPN algorithm. The addition of RXTE in 1995 also helped. Although RXTE was an X-ray mission in Earth orbit, it could detect those gamma-ray bursts which also shone in X-rays, and give a direction (rather than merely a time trigger) for them. Two important developments occurred in 1996. NEAR was launched; its trajectory to an asteroid again formed

141-515: A narrow-angle telescope, and has a limited ability to spin itself to place a GRB within the telescope field. MESSENGER 's Gamma Ray Neutron Spectrometer was able to add data to the IPN, before the end of MESSENGER's mission in 2015. Due to falling power from its RTG , Ulysses was decommissioned on June 30, 2009. Gamma rays Too Many Requests If you report this error to the Wikimedia System Administrators, please include

188-406: A solid-fuel Transfer Orbit Stage placed the spacecraft into an 11-month, Mars transfer trajectory, at a final speed of 5.28 km/s with respect to Mars. On August 25, 1992, particulate contamination was found within the spacecraft. After a full inspection, a cleaning was determined necessary and was performed on August 29. The suspected cause of the contamination were measures taken to protect

235-487: A time delay would occur between spacecraft triggers. In addition, each satellite had multiple gamma-ray detectors across their structures; the detectors facing a blast would register a higher gamma count than the detectors facing away. A gamma-ray burst was detected by the Vela group on June 3, 1969, and thus referred to as GRB 690603. The location was determined to be clearly outside of the satellites' orbit, and probably outside of

282-515: A triangular IPN measured in AUs. The IPN was also joined by BeppoSAX . BeppoSAX had wide-field gamma detectors, and narrow-field X-ray telescopes. Once a GRB was detected, operators could spin the spacecraft within hours to point the X-ray telescopes at the coarse location. The X-ray afterglow would then give a fine location. In 1997, the first fine location allowed detailed study of a GRB and its environ. Compton

329-491: Is almost always a ground station in view of the spacecraft, which reduces latency to seconds. The Swift spacecraft, launched in 2004, is similar in operation but much more powerful. When a GRB triggers the gamma detectors, generating a crude position, the spacecraft spins relatively rapidly to use its focusing X-ray and optical telescopes. These refine the GRB location to within arcminutes, and often within arcseconds. The fine position

376-476: Is now in a heliocentric orbit . On January 4, 1994, an independent investigation board from the Naval Research Laboratory , announced their findings: the most probable cause in the loss of communication was a rupture of the fuel pressurization tank in the spacecraft's propulsion system. It is believed that hypergolic fuel may have leaked past valves in the system during the cruise to Mars, allowing

423-511: Is reported to the ground in approximately an hour. INTEGRAL is a successor to Compton. INTEGRAL can similarly determine a coarse position by comparing gamma counts from one side to another. It also possesses a gamma-ray telescope with an ability to determine positions to under a degree. INTEGRAL cannot pivot rapidly like the small HETE and Swift spacecraft. But should a burst happen to occur in its telescope field of view, its position and characteristics can be recorded with high precision. RHESSI

470-789: The Compton Gamma-Ray Observatory in 1991 again formed triangular baselines with PVO and Ulysses. Ulysses continued until June 2009, and the PVO mission ended in August 1992. Compton once again brought directional discrimination with the BATSE instrument. Like the Velas, BATSE placed detectors at the spacecraft corners. Thus, Compton alone could determine a coarse burst location, to within 1.6 to 4 degrees. Baselines with other spacecraft were then used to sharpen Compton's position solutions. In addition, almost half

517-513: The Chinese and Indian detectors were operational for only a few months. Of all the above, Ulysses is the only spacecraft whose orbit takes it large distances away from the ecliptic plane. These deviations from the ecliptic plane allow more precise 3-D measurements of the apparent positions of the GRBs. New techniques and designs in high-energy astronomy spacecraft are challenging the traditional operation of

SECTION 10

#1732858301937

564-536: The IPN. Because distant probes require sensitive ground antennas for communication, they introduce a time lag into GRB studies. Large ground antennas must split time between spacecraft, rather than listen continuously for GRB notifications. Typically, GRB coordinates determined by deep space probes are distributed many hours to a day or two after the GRB. This is very frustrating for studies of events which are measured in seconds. A new generation of spacecraft are designed to produce GRB locations on board, then relay them to

611-793: The March 5, 1979, hard X-ray burst at ~10:51 EST, followed 11 s later by Helios 2 in orbit around the Sun, then the Pioneer Venus Orbiter at Venus. Seconds later the Vela satellites , Prognoz 7, and the Einstein Observatory in orbit around Earth were inundated. The last satellite hit was the ISEE-3 before the burst exited the Solar System . Pioneer Venus Orbiter was rejoined by Ulysses in 1990. The launch of

658-593: The Martian surface. Uses the components of the on-board telecommunications system and the stations of the Deep Space Network to collect data on the nature of the magnetic field and interactions the field may have with solar wind . Collects data on the gravity field and the Martian atmospheric structure with a special emphasis on temporal changes near the polar regions. Planned as augmentation to return data from

705-453: The OGO, OSO, and IMP series) had detectors for Earth, Solar, or all-sky gamma radiation, and also confirmed the GRB phenomenon. Scientists began to tailor instruments specifically for GRBs. The Helios-2 spacecraft carried a detector with precision time resolution to a Solar orbit that took it over one AU from Earth. Helios-2 was launched in 1976. In 1978, multiple spacecraft were launched, forming

752-607: The Solar system. After reviewing archived Vela data, a previous burst was determined to have occurred on July 2, 1967. Public reports of initial GRBs were not disclosed until the early 1970s. Additional spacecraft were given gamma-ray detectors. The Apollo 15 and 16 missions carried detectors to study the Moon; middle-to-late Venera spacecraft carried detectors to Venus. The relatively long baselines of these missions again showed that bursts originated at great distances. Other spacecraft (such as

799-616: The Venus atmosphere in 1992, but not enough other spacecraft were functioning to form the required baselines. On March 5 and 6, 1979, two bursts of hard X-rays were detected from the same source in the constellation Dorado by the γ-ray burst detector Konus , on the Venera 11 and Venera 12 spacecraft. These X-ray bursts were detected by several other spacecraft. As part of the InterPlanetary Network (IPN), Venera 11 , Venera 12 were hit by

846-464: The bipropellant thrusters to slow the spacecraft, entering into a highly elliptical orbit. Over the next three months, subsequent "transfer to lower orbit" (TLO) maneuvers would be performed as the spacecraft reached periapsis , eventually resulting in an approximately circular, 118-minute orbit around Mars. The primary mission was to begin on November 23, 1993, collecting data during one Martian year (approximately 687 Earth days). The first global map

893-422: The blanket in an unsymmetrical manner, resulting in a net spin rate. This high spin rate would cause the spacecraft to enter into the "contingency mode," which interrupted the stored command sequence and thus, did not turn the transmitter on. Additionally, this high spin rate precluded proper orientation of the solar arrays, resulting in discharge of the batteries. However, the spin effect may be academic, because

940-402: The board reported that the most probable cause of the loss of communications with the spacecraft on August 21, 1993, was a rupture of the fuel (monomethyl hydrazine (MMH)) pressurization side of the spacecraft's propulsion system, resulting in a pressurized leak of both helium gas and liquid MMH under the spacecraft's thermal blanket. The gas and liquid would most likely have leaked out from under

987-399: The boundaries between networks are defined differently by different commentators. Spacecraft naturally join or leave service as their missions unfold, and some modern spacecraft are far more capable than prior IPN members. The Vela group of satellites was originally designed to detect covert nuclear tests, possibly at the Moon's altitude. Thus, the Velas were placed in high orbits, so that

SECTION 20

#1732858301937

1034-477: The common pressurization system. During interplanetary cruise, the vapor mix had accumulated in feed lines and pressurant lines, resulting in explosion and their rupture after the engine was restarted for routine course correction. A similar problem later crippled the Akatsuki space probe in 2010. Although none of the primary objectives were achieved, the mission provided interplanetary cruise phase data, collected up to

1081-421: The composition of clouds. Uses narrow-band radiometric channels and two pressure modulation cells to measure atmospheric and surface emissions in the thermal infrared and a visible channel to measure dust particles and condensates in the atmosphere and on the surface at varying longitudes and seasons. Records the spectrum of gamma rays and neutrons emitted by the radioactive decay of elements contained in

1128-467: The date of last contact. This data would be useful for subsequent missions to Mars. Science instruments originally developed for Mars Observer were placed on four subsequent spacecraft to complete the mission objectives: Mars Global Surveyor launched in 1996, Mars Climate Orbiter launched in 1998, 2001 Mars Odyssey launched in 2001 and Mars Reconnaissance Orbiter launched in 2005. On August 24, 1993, Mars Observer would turn 180 degrees and ignite

1175-554: The details below. Request from 172.68.168.132 via cp1112 cp1112, Varnish XID 388865283 Upstream caches: cp1112 int Error: 429, Too Many Requests at Fri, 29 Nov 2024 05:31:42 GMT Mars Observer The Mars Observer spacecraft, also known as the Mars Geoscience/Climatology Orbiter , was a robotic space probe launched by NASA on September 25, 1992, to study the Martian surface, atmosphere, climate and magnetic field. On August 21, 1993, during

1222-436: The development matured, the primary science objectives were finalized as: The program's total cost is estimated at $ 813 million. The Mars Observer spacecraft had a mass of 1,018 kilograms (2,244 lb). Its bus measured 1.1 meters tall, 2.2 meters wide, and 1.6 meters deep. The spacecraft was based on previous satellite designs, originally intended and developed to orbit Earth. The RCA AS-4000 Ku-band satellite design

1269-401: The digital tape recorders and played back to Earth each day. Over 75  gigabytes of scientific data was expected to be yielded during the primary mission, much more than any previous mission to Mars. The end of the operable life for the spacecraft was expected to be limited by the supply of propellant and the condition of the batteries. On August 21, 1993, at 01:00 UTC, three days prior to

1316-404: The distinction between 2nd, 3rd, and subsequent IPNs is semantic. Compton and Ulysses were joined by Wind in 1994. Although Wind was in Earth orbit, like Compton, its altitude was very high, thus forming a short but usable baseline. The high altitude also meant that Earth blockage was negligible. In addition, Wind carried a top and bottom detector. Interpolation between the two units usually gave

1363-481: The fuel and oxidizer to combine prematurely before reaching the combustion chamber. The leaking fuel and gas probably resulted in a high spin rate, causing the spacecraft to enter into the "contingency mode"; this interrupted the stored command sequence and did not turn the transmitter on. The engine was derived from one belonging to an Earth orbital satellite and was not designed to lie dormant for months before being fired. However, after conducting extensive analyses,

1410-403: The ground within minutes or even seconds. These positions are based not on time correlation, but on X-ray telescopes, as on BeppoSAX but much faster. HETE -2, launched in 2000, stares at a large region of sky. Should a GRB trigger the gamma detectors, X-ray masks report sky coordinates to ground stations. Because HETE is in a low, consistent orbit, it can use many inexpensive ground stations. There

1457-486: The information already gathered by the Viking program . Preliminary mission goals expected the probe to provide planetary magnetic field data, detection of certain spectral line signatures of minerals on the surface, images of the surface at 1 meter / pixel and global elevation data. Mars Observer was originally planned to be launched in 1990 by a Space Shuttle Orbiter. The possibility for an expendable rocket to be used

InterPlanetary Network - Misplaced Pages Continue

1504-566: The interplanetary cruise phase, communication with the spacecraft was lost, three days prior to the probe's orbital insertion . Attempts to re-establish communications with the spacecraft were unsuccessful. In 1984, a high priority mission to Mars was set forth by the Solar System Exploration Committee. Then titled the Mars Geoscience/Climatology Orbiter , the Martian orbiter was planned to expand on

1551-399: The mission. Consists of narrow-angle and wide-angle telescopic cameras to study the meteorology/climatology and geoscience of Mars. A laser altimeter used to define the topography of Mars . Uses three sensors (Michelson interferometer, solar reflectance sensor, broadband radiance sensor) to measure thermal infrared emissions to map the mineral content of surface rocks, frosts and

1598-579: The more sophisticated the "staring" instrument, the lower the sky coverage. Randomly occurring GRBs are more likely to be missed, or detected at low resolution only. The use of non-directional deep space probes, such as MESSENGER and BepiColombo , will continue. In 2007 AGILE was launched and in 2008 the Fermi Gamma-ray Space Telescope and although these are Earth orbiters, their instruments provide directional discrimination. The Fermi Space Telescope uses both wide-area burst detectors and

1645-457: The necessary baselines for a position determination. The Pioneer Venus Orbiter and its Soviet counterparts, Venera 11 and 12 , took gamma detectors to the orbit of Venus. In addition, the spacecraft Prognoz-7 and ISEE-3 remained in Earth orbit. These formed an Earth-Venus-Sun triangle, and the probes at Venus formed a smaller triangle. 84 bursts were detected, until the network degraded in 1980. The Pioneer Venus Orbiter continued until it entered

1692-771: The penetrators and surface stations of the Russian Mars '94 mission and from penetrators, surface stations, a rover, and a balloon from the Mars '96 mission. Mars Observer was launched on September 25, 1992, at 17:05:01 UTC by the National Aeronautics and Space Administration from Space Launch Complex 40 at the Cape Canaveral Air Force Station in Florida, aboard a Commercial Titan III CT-4 launch vehicle. The complete burn sequence lasted for 34 minutes after

1739-439: The planet, horizon sensors indicate the orientation of the spacecraft while the reaction wheels would maintain the orientation of the instruments, towards Mars. The chosen orbit was also Sun-synchronous, allowing the daylit side of Mars to always be captured during the mid-afternoon of each Martian Sol . While some instruments could provide a real-time data link when Earth was in view of the spacecraft, data would also be recorded to

1786-452: The released MMH would likely attack and damage critical electrical circuits within the spacecraft. The board's study concluded that the propulsion system failure most probably was caused by the inadvertent mixing and the reaction of nitrogen tetroxide (NTO) and MMH within titanium pressurization tubing, during the helium pressurization of the fuel tanks. This reaction caused the tubing to rupture, resulting in helium and MMH being released from

1833-401: The scheduled Mars orbital insertion , there was an "inexplicable" loss of contact with Mars Observer . New commands were sent every 20 minutes in the hopes that the spacecraft had drifted off course and could regain contact. However, the attempt was unsuccessful. It is unknown whether the spacecraft was able to follow its automatic programming and go into Mars orbit or if it flew by Mars and

1880-594: The sky from Compton was blocked by the Earth, just as Venus blocked part of the sky for PVO. Detection or non-detection by Compton or PVO added another element to the location algorithms. Compton also had high-precision, low-field-of-view gamma instruments. Occasionally, GRBs would occur where Compton happened to be pointing. The use of multiple, sensitive instruments would provide much more accuracy than BATSE alone. Compton and Ulysses were joined briefly by Mars Observer in late 1992, before that spacecraft failed. Some feel that Compton provided sufficient continuity, and that

1927-448: The sky. Some forms of gamma ray telescope can generate an image, but they require longer integration times, and cover only a fraction of the sky. Once three spacecraft detect a GRB, their timings are sent to the ground for correlation. A sky position is derived, and distributed to the astronomical community for follow-up observations with optical, radio, or spaceborne telescopes. Note that, since any IPN must consist of several spacecraft,

InterPlanetary Network - Misplaced Pages Continue

1974-406: The spacecraft prior to the landfall of Hurricane Andrew which struck the coast of Florida on August 24. Mars Observer was scheduled to perform an orbital insertion maneuver on August 24, 1993, but contact with the spacecraft was lost on August 21, 1993. The likely reason for the spacecraft failure was the leakage of fuel and oxidizer vapors through the improperly designed PTFE check valve to

2021-470: Was also suggested, if the spacecraft was designed to meet certain constraints. On March 12, 1987, the mission was rescheduled for launch in 1992, in lieu of other backlogged missions ( Galileo , Magellan , Ulysses ) after the Space Shuttle Challenger disaster . Along with a launch delay, budget overruns necessitated the elimination of two instruments to meet the 1992 planned launch. As

2068-728: Was deorbited in 2000; the NEAR mission was shut down in early 2001. In late 2001, the Mars Odyssey spacecraft again formed an interplanetary triangle. Other members of the network include or have included the Indian SROSS-C2 spacecraft, the US Air Force's Defense Meteorological Satellites, the Japanese Yohkoh spacecraft, and the Chinese SZ-2 mission. These have all been Earth orbiters, and

2115-415: Was expected to be completed on December 16, followed by solar conjunction beginning on December 20, and lasting for nineteen days, ending on January 3, 1994; during this time, mission operations would be suspended as radio contact would not be possible. Orbiting Mars at an approximate speed of 3.4 km/s, the spacecraft would travel around Mars in a north to south, polar orbit. As the spacecraft circles

2162-477: Was launched in 2002 to perform solar studies. However, its gamma instrument could detect bright gamma sources from other regions of the sky, and produce coarse positions through differential detectors. Occasionally, a GRB would appear next to the Sun, and the RHESSI instrument would determine its properties without IPN assistance. Note however, that all these spacecraft suffer from Earth blockage to varying degrees. Also,

2209-472: Was used extensively for the spacecraft bus, propulsion, thermal protection, and solar array. RCA TIROS and DMSP Block 50-2 satellite designs were also utilized in the implementing the Attitude and Articulation Control System (AACS), command and data handling subsystem, and power subsystem, into Mars Observer . Other elements such as the bipropellant components and high-gain antenna were designed specifically for

#936063