Names | IMP-J IMP-8 Interplanetary Monitoring Platform-8 |
---|---|
Mission type | Space physics |
Operator | NASA |
COSPAR ID | 1973-078A |
SATCAT no. | 06893 |
Mission duration | 34 years (achieved) 51 years, 20 days (in orbit) |
Spacecraft properties | |
Spacecraft | Explorer L |
Spacecraft type | Interplanetary Monitoring Platform |
Bus | IMP |
Manufacturer | Goddard Space Flight Center |
Launch mass | 371 kg (818 lb) [1] |
Dimensions | Polyhedron of 16 faces: 157.4 cm (62.0 in) height 135.6 cm (53.4 in) diameter |
Power | 150 watts |
Start of mission | |
Launch date | 26 October 1973, 02:26:03 UTC [2] |
Rocket | Thor-Delta 1604 (Thor 582 / Delta 097) |
Launch site | Cape Canaveral, LC-17B |
Contractor | Douglas Aircraft Company |
Entered service | 26 October 1972 |
End of mission | |
Deactivated | October 2001 |
Last contact | 7 October 2006 |
Orbital parameters | |
Reference system | Geocentric orbit [3] |
Regime | High Earth orbit |
Perigee altitude | 22.11 RE |
Apogee altitude | 45.26 RE |
Inclination | 28.64° |
Period | 11.99 days |
Instruments | |
Charged Particle Measurements Experiment (CPME) Cosmic Ray Nuclear Composition Electrons, Hydrogen and Helium Isotopes Electrostatic Fields Electrostatic Waves and Radio Noise Energetic Electrons and Protons Magnetic Field Experiment Measurement of Low-Energy Protons and Electrons Solar and Cosmic-Ray Particles Solar Plasma Electrostatic Analyzer Solar Plasma Faraday Cup | |
Explorer 50, also known as IMP-J or IMP-8, was a NASA satellite launched to study the magnetosphere. It was the eighth and last in a series of the Interplanetary Monitoring Platform . [4]
Explorer 50 was a drum-shaped spacecraft, 135.6 cm (53.4 in) across and 157.4 cm (62.0 in) height, with propulsion Star-17A , instrumented for interplanetary medium and magnetotail studies of cosmic rays, energetic solar particles, plasma, and electric and magnetic fields. Its initial orbit was more elliptical than intended, with apogee and perigee distances of about 45.26 Earth radii and 22.11 Earth radii. Its orbital eccentricity decreased after launch. Its orbital inclination varied between 0 deg and about 55° with a periodicity of several years. The spacecraft spin axis was normal to the ecliptic plane, and the spin rate was 23 rpm. The data telemetry rate was 1600 bit/s. The spacecraft was in the solar wind for 7 to 8 days of every 11.99 days orbit. Telemetry coverage was 90% in the early years, but only 60-70% through most of the 1980s and early 1990s. Coverage returned to the 90% range in the mid to late 1990s. [5]
Explorer 50 was launched on 23 October 1973 at 02:26:03 UTC, by a Thor-Delta 1604 launch vehicle from Cape Canaveral (CCAFS), Florida. [2] [6] The spacecraft functioned nominally until 7 October 2006. The satellite orbited the Earth once every 12 days, at an inclination of 28.67°. Its perigee was 25 Earth radii and apogee was 45 Earth radii. [5]
Three solid-state detectors in an anticoincidence plastic scintillator observed electrons between 0.2 and 2.5 MeV; protons between 0.3 and 500 MeV; alpha particles between 2.0 and 200 MeV; heavy particles with Z values ranging from 2 to 5 with energies greater than 8 MeV; heavy particles with Z values ranging between 6 and 8 with energies greater than 32 MeV; and integral protons and alphas of energies greater than 50 MeV/nucleon, all with dynamic ranges of 1 to 1E+6 particles per (cm2-second-sr). Five thin-window Geiger–Müller tubes observed electrons of energy greater than 15 keV, protons of energy greater than 250 keV, and X-rays with wavelengths between 2 and 10 A, all with a dynamic range of 10 to 1E+8 per (cm2-second-sr). Particles and X-rays, primarily of solar origin, were studied, but the dynamic range and resolution of the instrument also permitted observation of cosmic rays and magnetotail particles. [7]
This experiment used two telescopes to measure the composition and energy spectra of solar (and galactic) particles above about 0.5 MeV/nucleon. The main telescope consisted of five collinear elements (three solid state, one Caesium iodide (CsI), and one sapphire Cherenkov) surrounded by a plastic anticoincidence shield. The telescope had a 60°, full-angle acceptance cone with its axis approximately normal to the spacecraft spin axis, permitting eight-sectored information on particle arrival direction. Four elements of the main telescope were pulse-height analyzed, and low- and high-gain modes could be selected by command to permit resolution of the elements Hydrogen (H) through Nickel (Ni) or of electrons and the isotopes of Hydrogen (H) and Helium (He) and light nuclei. A selection-priority scheme was included to permit sampling of less abundant particle species under normal and solar-flare conditions. The low-energy telescope was essentially a two-element shielded solid-state detector with a 70° full-angle acceptance cone. The first element was pulse-height analyzed, and data were recorded by sectors. [8]
This experiment was designed to measure the differential energy spectra of the isotopes of hydrogen through oxygen from 2 to 40-MeV/nucleon, and of electrons from 0.2 to 5-MeV. The instrument consisted of a stack of 11 fully depleted silicon solid-state detectors surrounded by a plastic scintillator anticoincidence cup. The outer two solid-state detectors were annular, permitting measurements in both narrow-geometry (typical geometrical factor was 0.2 cm2-sr) and wide-geometry (typical geometric factor was 1.5 cm2-sr) coincidence modes. Anisotropy data (45° angular and 20 seconds temporal resolution) were obtained. [9]
The instrument was designed to measure ambient electric fields in the solar wind and the Earth's magnetosheath up to 1 kHz in frequency. The sensor consisted of a pair of 70 m (230 ft) wire antennas (140 m (460 ft), tip-to-tip), which were held rigid by centrifugal force due to satellite spin (about 24 rpm). The wires were insulated from the plasma, except for their short outer sections, to remove the active probe area from the spacecraft sheath. The antenna served as a double floating probe, and measurements were obtained every 1/4 spacecraft revolution (about 0.75 second). Ultra low frequency (ULF) and Very low frequency (VLF) measurements were obtained using seven 60% bandwidth filters with center frequencies logarithmically spaced from 1-Hz to 1000-Hz. These frequency channels had an intrinsic sensitivity of 1.0E-5 V/m, and a peak range of 1.0E-2 V/m. However, the effective low-frequency filter threshold was determined by interference due to harmonics of the spacecraft spinning within an asymmetric sheath. The other major limitation was also due to sheath effect. Whenever the electron plasma density was less than about 10 particles/cc, the sheath overlapped the active antenna portions and precluded meaningful measurements of ambient conditions. [10]
A wide-band receiver was used to observe high-resolution frequency-time spectra, and a six-channel narrow-band receiver with a variable center frequency was used to observe wave characteristics. The receivers operated from three antenna systems. The first system contained a pair of long dipole antennas (one, extendable to about 124 m (407 ft), normal to the spacecraft spin axis and the other antenna, extendable to about 6.1 m (20 ft), along the spin axis). The second system contained a boom-mounted triad of orthogonal loop antennas. The third system consisted of a boom-mounted 0.51 m (1 ft 8 in) spin-axis dipole. The magnetic and electric field intensities and frequency spectra, polarization, and direction of arrival of naturally occurring radio noise in the magnetosphere were observed. Phenomena studied were the time-space distribution, origin, propagation, dispersion, and other characteristics of radio noise occurring across and on either side of the magnetospheric boundary region. The frequency range for electric fields was 0.3 Hz to 200 kHz, and for magnetic fields it was 20 Hz to 200 kHz. [11]
The purposes of this investigation were: (1) to study the propagation characteristics of solar cosmic rays through the interplanetary medium over the energy ranges indicated below, (2) to study electron and proton fluxes throughout the geomagnetic tail and near the flanks of the magnetosphere and (3) to study the entry of solar cosmic rays into the magnetosphere. The instrumentation consisted of a three-element telescope employing fully depleted surface-barrier solid-state detectors and a magnet to deflect electrons. Two side-mounted detectors were used to measure the deflected electrons. Two additional detectors in separate mounts were used to measure charged particles above 15 keV (F), Z greater than or equal to 2 above 0.6 MeV (G1) and above 1.0 MeV (G2), and Z greater than or equal to 3 above 2.0 MeV (G3). The telescope measured protons in three ranges between 2.1 and 25 MeV (14, 15, 16 channels); Z greater than or equal to 1 in three ranges between 0.05 and 2.1 MeV (11, 12, 13 channels); alpha particles between 8.4 and 35.0 MeV in two ranges (111, 112 channels); Z greater than or equal to 2 between 2.2 and 8.4 MeV (110 channel); and a background channel (19 channel). Deflected electrons were measured in two ranges between 30 and 200 keV (17, 18 channels). [12]
This experiment consisted of a boom-mounted triaxial fluxgate magnetometer designed to study the interplanetary and geomagnetic tail magnetic fields. Each sensor had three dynamic ranges of ± 12, ± 36, and ± 108 nT. With the aid of a bit compaction scheme (delta modulation), 25 vector measurements were made and telemetered per second. The experiment operated normally from launch until mid-1975. On 11 July 1975, because of a range indicator problem, the experiment operation was frozen into the 36 nT range. The digitization accuracy in this range is about ± 0.3 nT. On 23 March 1978, the sensor flipper failed. After that time, alternative methods of Z-axis sensor zero-level determination were required. The magnetometer failed 10 June 2000. [13]
This experiment was designed to measure the energy spectra of low-energy electrons and protons in the geocentric range of 30 to 40 Earth radii to give further data on geomagnetic storms, aurora, tail and neutral sheet, and other magnetospheric phenomena. The detector was a dual-channel, curved-plate electrostatic analyzer (LEPEDEA - low energy proton and electron differential energy analyzer) with 16 energy intervals between 5 eV and 50 keV. It had an angular field of view of 9° by 25°. The detector could be operated in one of two modes: (1) one providing good angular resolution (16 directions for each particle energy band) once each 272 seconds, and (2) the other providing good temporal resolution in which the entire energy range in four directions was measured every 68 seconds. [14]
The Goddard Space Flight Center cosmic-ray experiment was designed to measure energy spectra, composition, and angular distributions of solar and galactic electrons, protons, and heavier nuclei up to Z=30. Three distinct detector systems were used. The first system consisted of a pair of solid-state telescopes that measured integral fluxes of electrons above 150, 350 and 700 keV and of protons above 0.05, 0.15, 0.50, 0.70, 1.0, 1.2, 2.0, 2.5, 5.0, 15, and 25 MeV. Except for the 0.05 MeV proton mode, all counting modes had unique species identification. The second detector system was a solid-state dE/dx versus E telescope that looked perpendicular to the spin axis. This telescope measured Z=1 to 16 nuclei with energies between 4 and 20 MeV/nucleon. Counts of particles in the 0.5 to 4 MeV/nucleon range, with no charge resolution, were obtained as counts in the dE/dx sensor but not in the E sensor. The third detector system was a three-element telescope whose axis made an angle of 39° with respect to the spin axis. The middle element was a CsI scintillator, while the other two elements were solid-state sensors. The instrument responded to electrons between 2 and 12 MeV and to Z=1 to 30 nuclei in the energy range 20 to 500 MeV/nucleon. For particles below 80 MeV, this instrument acted as a dE/dx versus E detector. Above 80 MeV, it acted as a bidirectional triple dE/dx versus E detector. Flux directionality information was obtained by dividing certain portions of the data from each detector into eight angular sectors. [15]
A hemispherical electrostatic analyzer measured the directional intensity of positive ions and electrons in the solar wind, magnetosheath, and magnetotail. Ions as heavy as oxygen were resolved when the solar wind temperature was low. Energy analysis was accomplished by charging the plates to known voltage levels and allowing them to discharge with known RC time constants. In the solar wind, positive ions from 200-eV to 5 keV (15% spacing, 3% resolution) and electrons from 5 eV to 1 keV (30% spacing, 15% resolution) were studied. In the magnetosheath, positive ions from 200 eV to 5 keV (15% spacing, 3% resolution) and from 200 eV to 20 keV (30% spacing, 15% resolution) and electrons from 5 eV to 1 keV (30% spacing, 15% resolution) were studied. In the magnetotail, positive ions from 200 eV to 20 keV (30% spacing, 15% resolution) and electrons from 5 eV to 1 keV (30% spacing, 15% resolution) and from 100 eV to 20 keV (15% resolution) were studied. No data were obtained from this experiment past October 2001. [16]
A modulated split-collector Faraday cup, perpendicular to the spacecraft spin axis, was used to study the directional intensity of positive ions and electrons in the solar wind, transition region, and magnetotail. Electrons were studied in eight logarithmically equispaced energy channels between 17 eV and 7 keV. Positive ions were studied in eight channels between 50 eV and 7 keV. A spectrum was obtained every eight spacecraft revolutions. Angular information was obtained in either 15 equally spaced intervals during a 360° revolution of the satellite or in 15 angular segments centered more closely about the spacecraft-sun line. [17]
This experiment was designed to determine the composition and energy spectra of low-energy particles observed during solar flares and 27-d recurrent events. The detectors used included: (1) an electrostatic analyzer (to select particles of the desired energy per charge) combined with an array of windowless solid-state detectors (to measure the energy loss) and surrounded by an anticoincidence shield and (2) a thin-window proportional counter, solid-state particle telescope. The experiment measured particle energies from 0.1 to 10 MeV per charge in 12 bands and uniquely identified positrons and electrons as well as nuclei with charges of Z from 1 to 8 (no charge resolution for Z greater than 8). Two 1000-channel pulse-height analyzers, one for each detector, were included in the experiment payload. [18]
The objectives of the extended Explorer 50 (IMP-8) operations were to provide solar wind parameters as input for magnetospheric studies and as a 1-AU baseline for deep space studies, and to continue solar cycle variation studies with a single set of well-calibrated and understood instruments. [5]
In October 2001, Explorer 50 (IMP-8) was terminated as an independent mission. Telemetry acquisition resumed after about three months at Canberra, Australia, only (30-50% coverage), as an adjunct to the Voyager and Ulysses missions. The last useful science data from Explorer 50 (IMP-8) was acquired on 7 October 2006. [5]
Explorer 35,, was a spin-stabilized spacecraft built by NASA as part of the Explorer program. It was designed for the study of the interplanetary plasma, magnetic field, energetic particles, and solar X-rays, from lunar orbit.
Explorer 11 was a NASA satellite that carried the first space-borne gamma-ray telescope. This marked the beginning of space gamma-ray astronomy. Launched on 27 April 1961 by a Juno II, the satellite returned data until 17 November 1961, when power supply problems ended the science mission. During the spacecraft's seven-month lifespan it detected twenty-two events from gamma-rays and approximately 22,000 events from cosmic radiation.
Explorer 33, also known as IMP-D and AIMP-1, is a spacecraft in the Explorer program launched by NASA on 1 July 1966 on a mission of scientific exploration. It was the fourth satellite launched as part of the Interplanetary Monitoring Platform series, and the first of two "Anchored IMP" spacecraft to study the environment around Earth at lunar distances, aiding the Apollo program. It marked a departure in design from its predecessors, IMP-A through IMP-C. Explorer 35 was the companion spacecraft to Explorer 33 in the Anchored IMP program, but Explorer 34 (IMP-F) was the next spacecraft to fly, launching about two months before AIMP-E, both in 1967.
The Solar Anomalous and Magnetospheric Particle Explorer was a NASA solar and magnetospheric observatory and was the first spacecraft in the Small Explorer program. It was launched into low Earth orbit on 3 July 1992, from Vandenberg Air Force Base aboard a Scout G-1 launch vehicle. SAMPEX was an international collaboration between NASA and the Max Planck Institute for Extraterrestrial Physics of Germany. The Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) is the first of a series of spacecraft that was launched under the Small Explorer (SMEX) program for low-cost spacecraft.
Explorer 18, also called IMP-A, IMP-1, Interplanetary Monitoring Platform-1 and S-74, was a NASA satellite launched as part of the Explorer program. Explorer 18 was launched on 27 November 1963 from Cape Canaveral Air Force Station (CCAFS), Florida, with a Thor-Delta C launch vehicle. Explorer 18 was the first satellite of the Interplanetary Monitoring Platform (IMP). Explorer 21 (IMP-B) launched in October 1964 and Explorer 28 (IMP-C) launched in May 1965 also used the same general spacecraft design.
Explorer 14, also called EPE-B or Energetic Particles Explorer-B, was a NASA spacecraft instrumented to measure cosmic-ray particles, trapped particles, solar wind protons, and magnetospheric and interplanetary magnetic fields. It was the second of the S-3 series of spacecraft, which also included Explorer 12, 14, 15, and 26. It was launched on 2 October 1962, aboard a Thor-Delta launch vehicle.
The ISEE-1 was an Explorer-class mother spacecraft, International Sun-Earth Explorer-1, was part of the mother/daughter/heliocentric mission. ISEE-1 was a 340.2 kg (750 lb) space probe used to study magnetic fields near the Earth. ISEE-1 was a spin-stabilized spacecraft and based on the design of the prior IMP series of spacecraft. ISEE-1 and ISEE-2 were launched on 22 October 1977, and they re-entered on 26 September 1987.
The ISEE-2 was an Explorer-class daughter spacecraft, International Sun-Earth Explorer-2, was part of the mother/daughter/heliocentric mission. ISEE-2 was a 165.78 kg (365.5 lb) space probe used to study magnetic fields near the Earth. ISEE-2 was a spin-stabilized spacecraft and based on the design of the prior IMP series of spacecraft. ISEE-1 and ISEE-2 were launched on 22 October 1977, and they re-entered on 26 September 1987.
Explorer 12, also called EPE-A or Energetic Particles Explorer-A and as S3), was a NASA satellite built to measure the solar wind, cosmic rays, and the Earth's magnetic field. It was the first of the S-3 series of spacecraft, which also included Explorer 12, 14, 15, and 26. It was launched on 16 August 1961, aboard a Thor-Delta launch vehicle. It ceased transmitting on 6 December 1961 due to power failure.
Explorer 26 was a NASA satellite launched on 21 December 1964, as part of NASA's Explorer program. Its primary mission was to study the Earth's magnetic field.
Explorer 28, also called IMP-C, IMP-3 and Interplanetary Monitoring Platform-3, was a NASA satellite launched on 29 May 1965 to study space physics, and was the third spacecraft launched in the Interplanetary Monitoring Platform program. It was powered by chemical batteries and solar panels. There were 7 experiments on board, all devoted to particle studies. Performance was normal until late April 1967, when intermittent problems began. It stayed in contact until 12 May 1967, when contact was lost. The orbit decayed until it re-entered the atmosphere on 4 July 1968. The spacecraft design was similar to its predecessors Explorer 18 (IMP-A), launched in November 1963, and Explorer 21 (IMP-B), launched in October 1964, though this satellite was a few kilograms lighter. The successor Explorer 33 (IMP-D) began the use of a new design.
Explorer 15, also called EPE-C or Energetic Particles Explorer-C, was a NASA satellite launched as part of the Explorer program. Explorer 15 was launched on 27 October 1962, at Cape Canaveral Air Force Station, Florida, United States, with a Thor-Delta A.
Explorer 21, also called IMP-B, IMP-2 and Interplanetary Monitoring Platform-2, was a NASA satellite launched as part of Explorer program. Explorer 21 was launched on 4 October 1964, at 03:45:00 GMT from Cape Canaveral (CCAFS), Florida, with a Thor-Delta C launch vehicle. Explorer 21 was the second satellite of the Interplanetary Monitoring Platform, and used the same general design as its predecessor, Explorer 18 (IMP-A), launched the previous year, in November 1963. The following Explorer 28 (IMP-C), launched in May 1965, also used a similar design.
Explorer 25, was a NASA magnetically aligned satellite launched simultaneously with Explorer 24 (AD-B) using a Scout X-4 launch vehicle. This was NASA's first dual-satellite launch. The satellite's primary mission was to make measurements of the influx of energetic particles into the atmosphere of Earth and to study atmospheric heating and the increase in scale height which have been correlated with geomagnetic activity. Studies of the natural and artificial trapped Van Allen radiation belts were also conducted. A biaxial fluxgate magnetometer was used to monitor the orientation of the spacecraft with respect to the local magnetic field.
Explorer 34, was a NASA satellite launched as part of Explorer program. Explorer 34 as launched on 24 May 1967 from Vandenberg Air Force Base, California, with Thor-Delta E1 launch vehicle. Explorer 34 was the fifth satellite launched as part of the Interplanetary Monitoring Platform program, but was known as "IMP-4" because the preceding launch was more specifically part of the "Anchored IMP" sub-program. The spacecraft was put into space between the launches of Explorer 33 in 1966 and Explorer 35 in July 1967, but the next satellite to use Explorer 34's general design was Explorer 41, which flew in 1969.
Explorer 41, also called IMP-G and IMP-5, was a NASA satellite launched as part of the Explorers program. Explorer 41 launched on 21 June 1969 from Vandenberg AFB, California, with a Thor-Delta E1 launch vehicle. Explorer 41 was the seventh satellite launched as part of the overall Interplanetary Monitoring Platform series, though it received the post-launch designation "IMP-5" because two previous flights had used the "AIMP" designation instead. It was preceded by the second of those flights, Explorer 35, launched in July 1967. Its predecessor in the strict IMP series of launches was Explorer 34, launched in May 1967, which shared a similar design to Explorer 41. The next launch of an IMP satellite was Explorer 43 in 1971.
Explorer 43, also called IMP-I and IMP-6, was a NASA satellite launched as part of the Explorers program. Explorer 43 was launched on 13 March 1971 from Cape Canaveral Air Force Station (CCAFS) with a Thor-Delta M6 launch vehicle. Explorer 43 was the sixth satellite of the Interplanetary Monitoring Platform.
Explorer 45 was a NASA satellite launched as part of Explorer program. Explorer 45 was the only one to be released from the program Small Scientific Satellite.
Explorer 47, was a NASA satellite launched as part of the Explorers program. Explorer 47 was launched on 23 September 1972 from Cape Canaveral, Florida, with a Thor-Delta 1604. Explorer 47 was the ninth overall launch of the Interplanetary Monitoring Platform series, but received the launch designation "IMP-7" because two previous "Anchored IMP" flights had used "AIMP" instead.
AMPTE-Charge Composition Explorer, also called as AMPTE-CCE or Explorer 65, was a NASA satellite designed and tasked to study the magnetosphere of Earth, being launched as part of the Explorer program. The AMPTE mission was designed to study the access of solar wind ions to the magnetosphere, the convective-diffusive transport and energization of magnetospheric particles, and the interactions of plasmas in space.