Explorer 33

Explorer 33
NSSDC ID	1966-058A
Mission goal	Exploration of the magnetosphere
Client	NASA
Launcher	Delta-E
construction
Takeoff mass	212 kg
Course of the mission
Start date	July 1, 1966
launch pad	Cape Canaveral , LC-17B
End date	September 21, 1971

Explorer 33 (1966)

Explorer 33 (also known as AIMP 1 , IMP-D and 02258 ) was the US's first attempt to put a satellite into lunar orbit. There it should contribute to the research of the magnetic field, the plasma and energetic particles in the area around the moon . The Explorer 33 was launched on July 1, 1966, but could not be captured by the gravitational field of the moon due to a missile error and thus only reached one earth orbit. In spite of all this, the mission provided valuable data about the near-earth region.

Structure of the satellite

In addition to the standard systems for energy, thermal management, communication, etc., the satellite was equipped with seven experiments. The satellite systems are briefly described below.

The experiments

1. Experiment to measure ionizing radiation
   • Institution: University of California
   • Sensors: 1 × ionization chambers , 2 × Geiger-Müller counter tubes
   • The experiment was able to measure different energy levels of electrons and protons using three sensors. This should provide information about their occurrence, intensity and impact. This includes interplanetary ions and their relationship to magnetic storms , ions escaping from Earth via the magnetosphere, and observation of galactic cosmic rays .
2. Experiment to measure thermal ions and electrons
   • Sensor: Faraday cup
   • The experiment served to determine the number, intensity and temperature of the ions and electrons occurring.
3. Experiment to measure energetic particles
   • Institution: University of Iowa
   • Sensors: 1 × PN - semiconductor , 3 × Geiger-Müller counter tubes
   • The experiment should investigate the spatial, temporal and direction-dependent distribution of electrons in the earth's magnetic field at approx. 60 earth radii and the solar X-rays .
4. Experiment to measure the plasma flow in space
   • Institution: Massachusetts Institute of Technology
   • Sensors: Faraday cups
   • The experiment served to measure the properties of the plasma in space and time .
5. Experiment to measure the magnetic field
   • Institution: Ames Research Center
   • Sensors: 3 × Förster probes ( magnetometer )
   • The experiment served to measure the magnetic field in terms of strength and direction, as well as its spatial and temporal variations.
6. Experiment to measure the magnetic field
   • Institution: Goddard Space Flight Center (GSFC)
   • Sensors: 3 × Förster probes ( magnetometer )
   • The experiment should precisely measure the vector of the magnetic field on a spin-stabilized satellite. The aim was to measure the interplanetary and lunar magnetic fields and determine their interactions.
7. Experiment to measure the damage to solar cells
   • Institution: Goddard Space Flight Center (GSFC)
   • Sensors: 16 solar cells (1 × 2 cm) with 4 groups, thermistors (weight: 100 g)
   • The experiment examined various protective coatings for solar cells and their performance over time. For this purpose, various tests were carried out on the ground in order to be able to compare them with the measurements in orbit.

The satellite bus

The main focus in satellite development was on the environmental conditions during start-up (vibrations), commissioning (acceleration and deceleration to spin speed, unfolding the solar cells and magnetometer) and during the operation of the experiments. Further information on the satellite bus or the satellite follows:

• Structure: The AIMP had a modular structure in relation to the integration of the experiments. The materials aluminum , magnesium , nylon , POM and fiberglass were used due to weight savings and the non- magnetizable property. The structural weight corresponded to 15% of the starting weight.
• Thermal control system : Passive temperature regulation by means of appropriate surface coatings, insulation and selection of suitable materials.
• Orbit and position control : Spin stabilization process - the third upper stage accelerates the payload, after the second upper stage has burned out, to 150 1 / min and then carried out the third acceleration phase (injection into the transfer orbit to the moon). After the third upper stage burned out, the speed was reduced to 100 1 / min and reached around 27 1 / min after unfolding the solar cells and the magnetometer.
• Propulsion system : Solid-state propulsion with APCP as fuel that delivered a specific impulse (in a vacuum) of 275 s.
• Energy supply : Four solar panels with a corresponding battery and charge / discharge regulation system. The DC / DC converter provided voltages of 12, 20 and 28 V. The solar cells delivered a maximum of 66 W, whereby a maximum consumption of 52 W occurred.
• Telemetry and data system: Various encoders for the experiments and instruments, transmitter and antenna system.

findings

Through the GSFC magnetometer, the findings from the Explorer 18 (IMP-1, IMP-A) mission could be confirmed by Explorer 33. Explorer 18 measured the vectors of the earth's magnetic field between 7 and 30 earth radii. The deformation of the magnetosphere due to the solar wind could be determined from the measurements . The measurements showed a parallel alignment of the magnetic field to the sun-earth line (a kind of "magnetic field tail") at 30 earth radii (side facing away from the sun). This has already been identified by Explorer 10 and 14. On the side facing the sun, a shock front in the magnetosphere and the interplanetary magnetic field were identified. Explorer 33 was able to confirm this data. a. that the magnetic field tail is also present at 80 earth radii (~ 510,000 km, major semi-axis of the moon: 384,400 km).

In addition to measuring the magnetosphere, the probe was also able to record data relating to the protons occurring, the solar plasma, etc. and thus expand the knowledge of the near-earth environmental conditions.

annotation

Differences in the orbit parameter information from NASA to other sources can be seen in the variation of these due to orbital disturbances on the part of the moon. These disturbances caused the perigee to fluctuate between 32,000 km and 200,000 km, the apogee between 400,000 km and 600,000 km and the inclination between 5 ° and 50 °. The differences in the mass data of 212 kg and 57.1 kg could not yet be identified, whereby the assumption is that one of the data takes the fuel mass into account. There are also differences in the indication of the error that occurred in the rocket stage (2nd or 3rd stage), so that it could not be captured by the lunar gravity field. Since there is no exact information about the delta rocket with which Explorer 33 was launched ( Explorer 29 with a Delta-E), no statement can be made in this regard.

The AMIP-D (Anchored Interplanetary Monitoring Platform) was originally supposed to achieve a lunar orbit with the parameters: lunar apogee of 6,440 km, lunar perigee of 1,288 km and a lunar inclination of 175 °.

Web links

• IMP in the Encyclopedia Astronautica (English)
• Explorer: IMP D, E (LAIMP 1, 2) at Gunter′s Space Page (English).

Individual evidence

1. ↑ Explorer 33. NASA , archived from the original on August 5, 2010 ; accessed on July 30, 2011 (English). 
2. ↑ ^{a b} Explorer 33 in the NSSDCA Master Catalog , accessed July 30, 2011.
3. ↑ ^{a b c} AIMP (IM_P-D) - Technical Summary Description. (PDF; 4.5 MB) NASA , March 1967, accessed on July 30, 2011 (English). 
4. ^ Ness, Norman F .: The Earth's Magnetic Tail. (PDF; 2.0 MB) NASA , December 1964, accessed on August 6, 2011 (English). 
5. ↑ Ness, Norman F .; et al .: Observation of the Earth's Magnetic Tail and Neutral Sheet at 510,000 km by Explorer 33. (PDF; 694 kB) NASA , November 1966, accessed on August 6, 2011 (English). 
6. ↑ See NASA publications on "Explorer 33". NASA , accessed August 6, 2011 . 
7. ↑ Explorer 33 - Trajectory Details in the NSSDCA Master Catalog, accessed July 30, 2011.
8. ↑ ^{a b} Ness, NF; et. all: Observations of the Earth's Magnetic Tail and Neutral Sheet at 510,000 Kilometers by Explorer 33. (PDF; 3.2 MB) Journal of Geophysical Research, February 1, 1967, accessed on July 30, 2011 . 
9. ↑ Astronautics and Aeronautics 1966 - Chronology on Science, Technology and Policy. (PDF; 13.9 MB) NASA , Science and Technology Division, Library Congress, 1967, accessed on August 6, 2011 .