Explorer 18

Last updated

Explorer 18
Explorer-18 IMP-A.jpg
Explorer-18 (IMP-A) satellite
NamesIMP-A
IMP-1
Interplanetary Monitoring Platform-1
S-74
Mission type Space physics
Operator NASA
COSPAR ID 1963-046A OOjs UI icon edit-ltr-progressive.svg
SATCAT no. 00693
Spacecraft properties
SpacecraftIMP
Manufacturer Goddard Space Flight Center
Launch mass138 kg (304 lb)
Power4 deployable solar arrays and batteries
Start of mission
Launch date27 November 1963,
02:30:01 GMT [1]
Rocket Thor-Delta C
(Thor 387 / Delta 021)
Launch site Cape Canaveral, LC-17B
Contractor Douglas Aircraft Company
Entered service27 November 1963
End of mission
Last contact10 May 1965
Decay date30 December 1965 [2]
Orbital parameters
Reference system Geocentric orbit [2]
Regime Highly elliptical orbit
Perigee altitude 4,395 km (2,731 mi)
Apogee altitude 192,003 km (119,305 mi)
Inclination 35.20°
Period 5606 minutes
Instruments

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. [3]

Contents

Mission

Launch of Thor-Delta C with Explorer 18 satellite Thor Delta C with Explorer 18 (Nov. 27 1963).jpg
Launch of Thor-Delta C with Explorer 18 satellite

Explorer 18 was a solar cell and chemical-battery powered spacecraft instrumented for interplanetary and distant magnetospheric studies of energetic particles, cosmic rays, magnetic fields, and plasmas. Initial spacecraft parameters included a local time of apogee of 10:20 hours, a spin rate of 22 rpm, and a spin direction of 115° right ascension and -25° declination. Each normal telemetry sequence of 81.9 seconds duration consisted of 795 data bits. After every third normal sequence there was an 81.9 seconds interval of rubidium vapor magnetometer analog data transmission. The spacecraft performed normally until 30 May 1964, then intermittently until 10 May 1965, when it was abandoned. The principal periods of data coverage were 27 November 1963 to 30 May 1964; 17 September 1964 to 7 January 1965; and 21 February 1965 to 25 March 1965; however, only the first of these periods was very useful. [4]

Experiments

Cosmic-Ray Range versus Energy Loss

A charged-particle, solid-state telescope was used to measure the range and energy loss of galactic and solar cosmic rays. The experiment was designed to study particle energies (energy per nucleon intervals approximately proportional to Z squared/A) and charge spectra (Z<=6). The detector was oriented normal to the spacecraft spin axis. The detector accumulators for each energy interval were telemetered six times every 5.46 minutes. Each accumulation period was about 40 seconds (the initial spacecraft spin period was about 2 seconds). The output from two 128-channel, pulse-height analyzers was obtained for one incident particle every 41 seconds and read out along with the detector accumulations. A malfunction limited alpha studies to particles with E>30 MeV. [5]

Cosmic Rays

This experiment consisted of two detector systems. The first was a dE/dx versus E telescope with thin and thick Caesium iodide (CsI) scintillators (one each) and an anticoincidence plastic scintillation counter. The telescope axis was normal to the spacecraft spin axis. Counts of particles penetrating the thin CsI scintillator and stopping in the thick CsI scintillator were accumulated during one 39.36-seconds interval every 5.46 minutes. The relative contribution to the count rate of various species (electrons between 3 and 12 MeV, ions with charge=1 or 2, atomic mass=1, 2, 3 or 4, and energy between 18.7 and 81.6 MeV/nucleon) and energy spectral information were determined by 512-channel pulse-height analysis performed simultaneously on the output of both CsI scintillators six times every 5.46 minutes. The second detector system consisted of two Geiger–Müller tube (GM) telescopes oriented parallel to and perpendicular to the spacecraft spin axis. Each telescope consisted of two colinear GM tubes. The parallel and perpendicular telescopes measured, respectively: 1) the sum of counts due to protons above 70 MeV and electrons above 6.5 MeV and 2) the sum of counts due to protons above 65 MeV and electrons above 6 MeV. Counts registered in any one of the four GM tubes were also accumulated. These omnidirectional counts were due to protons above 50 MeV plus electrons above 4 MeV. The parallel, perpendicular, and omnidirectional count rates were obtained for one 40-seconds accumulation interval during successive normal 81.9-seconds telemetry sequences. Thus, any one count rate was measured for 40 seconds once each 5.46 minutes. Both detector systems worked well from launch until 26 May 1964. [6]

Faraday Cup

A five-element, split-collector Faraday cup was used to measure solar wind particles in the following sequence: positive ions from 45 to 105 eV, positive ions from 95 to 235 eV, positive ions from 220 to 640 eV, positive ions from 560 to 1800 eV, electrons from 65 to 210 eV, and positive ions from 1700 to 5400 eV. The split plane of the collector was in the spin equatorial plane of the spacecraft. Measurements consisted of 22 instantaneous current samples, each separated by 0.16 seconds (spanning more than one satellite rotation). These measurements represented the sum of the current to the split collector, the maximum difference in current encountered during spacecraft rotation, and an identification of which half of the collector was maximum. The entire sequence required 2.8 minutes and was repeated every 5.5 minutes. The entrance cone for this Faraday cup had a half-angle of about 80°. Interference was encountered from refracted particles (with the most pronounced effect at about 70° incidence to cup normal), from secondary electrons, and from Ultraviolet radiation. [7]

Fluxgate Magnetometers

Each of two uniaxial fluxgate magnetometers, having dynamic ranges of ± 40 nT, sampled the magnetic field 30 times within each of six 4.8-seconds intervals every 5.46 minutes. Detector sensitivities were plus or minus 0.25 nT, and digitization uncertainty was plus or minus 0.40 nT. A rubidium vapor magnetometer was used to calibrate the instruments but did not produce any independently useful data sets. The instruments functioned normally throughout the useful life of the satellite and provided usable data through 30 May 1964. [8]

Ion Chamber and Geiger–Müller Counters

The instrumentation for this experiment, designed to measure fluxes of geomagnetically trapped particles, consisted of a 7.6 cm (3.0 in) diameter, Neher-type ionization chamber and two Anton 223 Geiger–Müller tubes. The ion chamber responded to electrons and protons with E>1 and E>17 MeV, respectively. Both Geiger–Müller tubes were mounted parallel to the spacecraft spin axis. One Geiger–Müller tube detected electrons, with E>45 keV, scattered off a gold foil. The acceptance cone for these electrons had a 61° full-angle, and its axis of symmetry made an angle of 59.5° with the spacecraft spin axis. This Geiger–Müller tube responded omnidirectionally to electrons and protons with E>6 and E>52 MeV, respectively. The second Geiger–Müller tube had no direct access to the space environment and responded omnidirectionally to background electrons and protons with E>6 and E>52 MeV, respectively. Pulses from the ion chamber were accumulated for 326.08 seconds and read out once every 327.68 seconds. Counts from the first Geiger–Müller tube were accumulated for 39.36 seconds and read out six times every 327.68 seconds. Counts from the second Geiger–Müller tube were accumulated for 39.36 seconds and read out five times every 327.68 seconds. This experiment performed normally from launch through 10 May 1965. [9]

Retarding Potential Analyzer

The retarding potential analyzer was a three-element planar Faraday cup. It was mounted normal to the spacecraft spin axis and had an effective look angle of 5 sr. Coarse and fine resolution modes were programmed for both ions and electrons. These modes consisted of 15 steps each for retarding voltages of 0 to 28 V and 0 to 100 V. The entire ion and electron sequence was repeated once every 10.92 minutes, and each 15-step spectral analysis required 5.4 seconds. The experiment operated for about 20 hours after launch, until a failure of a mechanical programmer switch terminated operations. The data were adversely affected by secondary electrons and no longer exist. [10]

Solar Wind Protons

A quadrispherical electrostatic analyzer with a current collector and an electrometer amplifier was used to detect and analyze the positive ion component of the incident plasma and to study its gross flow characteristics. Protons were analyzed in 14 energy channels between 0.025 and 16 keV. The instrument was mounted on the satellite equatorial plane and had a view angle of 15° in this plane and of 90° in the plane containing the spin axis. The satellite's equatorial plane was divided into three contiguous sectors (111.8°, 111.8° and 136.4°) by use of an optical aspect sensor. The peak flux in one sector was recorded at one analyzer plate potential per revolution of the satellite (no information about the position within the sector in which the peak flux occurred was retained). After 14 revolutions, all energy channels had been scanned, and the process was repeated for the next sector. A complete scan in energy and sector was repeated every 5.46 minutes. No data were obtained for the brief periods when the satellite was in the magnetosphere. The instrument operated well until April 1964 when it started operating intermittently. Its operation continued to degrade thereafter. [11]

Digital Data Processor

The satellite included a Digital Data Processor (DDP) telemetry system [12] which made the first use of integrated circuits on a flown spacecraft, predating both the D-37C computer used in the Minuteman II missile system and the Apollo Guidance Computer. [13] [14] The DDP allowed the different onboard digital experiments to store results into accumulators which were then read out on a repeating cycle and encoded into pulse-frequency modulation (PFM) signals to be sent to ground stations. [15] The accumulators totaled 105 bits, plus a 15-bit clock. [12] In addition to the digital data sent in PFM format, a little over half of the normal transmission cycle (9 of 16 "frames") was used for sending analog signals. [15]

The processor used Series 51 chips from Texas Instruments, specifically the SN510 (a clocked SR latch) and the SN514 (dual 3-input NAND/NOR gates), which both came in 8-pin flatpack packages and used resistor-capacitor-transistor logic (RCTL). [16] [17] However, only two transistors could be put onto a single dies at the time, [13] so multiple dies with the different logic components that had to be connected together by hand with tiny wires before being sealed up in the package, making them very expensive to produce. Early examples cost more than US$400 (equivalent to $4,000in 2023). [18]

See also

Related Research Articles

<span class="mw-page-title-main">Explorer 4</span> Satellite launched by the United States (1958)

Explorer 4 was an American satellite launched on 26 July 1958. It was instrumented by Dr. James van Allen's group. The Department of Defense's Advanced Research Projects Agency (ARPA) had initially planned two satellites for the purposes of studying the Van Allen radiation belts and the effects of nuclear explosions upon these belts, however Explorer 4 was the only such satellite launched as the other, Explorer 5, suffered launch failure.

<span class="mw-page-title-main">Explorer 35</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 6</span> NASA satellite of the Explorer program

Explorer 6, or S-2, was a NASA satellite, launched on 7 August 1959, at 14:24:20 GMT. It was a small, spherical satellite designed to study trapped radiation of various energies, galactic cosmic rays, geomagnetism, radio propagation in the upper atmosphere, and the flux of micrometeorites. It also tested a scanning device designed for photographing the Earth's cloud cover. On 14 August 1959, Explorer 6 took the first photos of Earth from a satellite.

<span class="mw-page-title-main">Explorer 11</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 5</span> United States satellite launched in 1958

Explorer 5 was a United States satellite with a mass of 17.43 kg (38.4 lb). It was the last of the original series of Explorer satellites built, designed, and operated by the Jet Propulsion Laboratory.

<span class="mw-page-title-main">Explorer 33</span> NASA satellite of the Explorer program (1966–)

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.

<span class="mw-page-title-main">Explorer 14</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">ISEE-2</span>

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.

<span class="mw-page-title-main">Explorer 12</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 26</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 28</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 15</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 21</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 25</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 34</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 40</span> NASA satellite of the Explorer program

Explorer 40, was a NASA magnetically aligned satellite launched simultaneously with Explorer 39 (AD-C) using a Scout B launch vehicle.

<span class="mw-page-title-main">Explorer 41</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 43</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 47</span> NASA satellite of the Explorer program

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.

<span class="mw-page-title-main">Explorer 50</span> NASA satellite of the Explorer program

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.

References

  1. ↑ "Launch Log". Jonathan's Space Report. 21 July 2021. Retrieved 31 October 2021.
  2. 1 2 "Trajectory: IMP-A 19643-046A". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain.
  3. ↑ "Explorer-series reference images" . Retrieved 4 July 2021.
  4. ↑ "Display: Explorer 18 (IMP-A) 1963-046A". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  5. ↑ "Experiment: Cosmic-Ray Range versus Energy Loss". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  6. ↑ "Experiment: Cosmic Rays". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  7. ↑ "Experiment: Faraday Cup". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  8. ↑ "Experiment: Fluxgate Magnetometers". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  9. ↑ "Experiment: Ion Chamber and Geiger–Müller Counters". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  10. ↑ "Experiment: Retarding Potential Analyzer". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  11. ↑ "Experiment: Solar Wind Protons". NASA. 28 October 2021. Retrieved 31 October 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  12. 1 2 Hosea D. White, Jr. (December 1966). Evolution of satellite PFM encoding systems from 1960 to 1965 (Report). NASA. Retrieved 4 July 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  13. 1 2 "Developing the first ICs to orbit Earth". Texas Instruments. 24 June 2021. Retrieved 4 July 2021.
  14. ↑ Butrica, Andrew J. (2015). "Chapter 3: NASA's Role in the Manufacture of Integrated Circuits" (PDF). In Dick, Steven J. (ed.). Historical Studies in the Societal Impact of Spaceflight. NASA. pp. 149-250 (237-42). ISBN   978-1-62683-027-1 . Retrieved 4 July 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  15. 1 2 Frank Piazza (March 1966). Computer Analysis of Interplanetary Monitoring Platform (IMP) Spacecraft Performance (Report). NASA. Retrieved 4 July 2021.PD-icon.svg This article incorporates text from this source, which is in the public domain .
  16. ↑ Microelectronic Device Data Handbook (Report). Vol. 2 - Manufacturer and specific device information. Prepared by ARINC Research Corporation. NASA. Retrieved 4 July 2021.{{cite report}}: CS1 maint: others (link)PD-icon.svg This article incorporates text from this source, which is in the public domain .
  17. ↑ Carol Byrd. "Electronics & Computing Technology of the mid-1950s – late 1960s: The Apollo Vintage". Slideshare. Retrieved 4 July 2021.
  18. ↑ AnubisTTP (16 November 2008). "Texas Instruments SN514 Integrated Circuit". Industrial Alchemy. Retrieved 4 July 2021.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.