Explorer 33

Explorer 33 (also known as AIMP 1, IMP -D and 02258 ) was to transport the first U.S. attempt a satellite into lunar orbit. There, this should contribute to the research of the magnetic field, the plasma and energetic particles in the environment of the moon. The Explorer 33 was launched on 1 July 1966 but could not be captured by the gravitational field of the moon rocket because of an error and thus only reached Earth orbit. The mission delivered in spite of all valuable data on the near-Earth space.

Construction 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 described in the following short.

The experiments

• Institution: University of California
• Sensors: 1x ionization chambers, 2x Geiger -Müller counter tubes
• The experiment could 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 relation to magnetic storms, the ions escape through the magnetosphere of the Earth and the observation of the galactic cosmic radiation.

• Sensor: Faraday cup
• The experiment was to determine the number, the intensity and the temperature of the ions and electrons occurring.

• Institution: University of Iowa
• Sensors: 1x PN semiconductor, 3x Geiger- Müller counter tubes
• The experiment was to examine the spatial, temporal and directional distribution of electrons in the Earth's magnetic field at about 60 Earth radii and solar X-rays.

• Institution: Massachusetts Institute of Technology
• Sensors: Faraday cup
• The experiment was measurement of the spatial and temporal properties of the plasma.

• Institution: Ames Research Center
• Sensors: 3x Ranger probes ( magnetometer)
• The experiment was measurement of the magnetic field with respect to the strength and direction, as well as the spatial and temporal variations.

• Institution: Goddard Space Flight Center ( GSFC )
• Sensors: 3x Ranger probes ( magnetometer)
• The experiment should accurately measure the vector of the magnetic field on a spin- stabilized satellite. The aim was to measure the interplanetary and lunar magnetic field and determine its interactions.

• Institution: Goddard Space Flight Center ( GSFC )
• Sensors: 16 solar cells ( 1x2 cm) of 4 groups, thermistors ( weight: 100 g)
• The experiment investigated various protective coatings for solar cells and their performance over time. This various tests have been carried out on the ground, in order to compare them with the measurements in the orbit can.

The satellite bus

The main focus in the development of satellites was the environmental conditions at the start (vibration), the start-up ( acceleration and deceleration of spin speed, unfolding the solar cells and magnetometer) and the operation of the experiments. In the following, further details on the satellite bus, or satellite:

• Structure: The AIMP was modular with respect to the integration of the experiments. There, the materials aluminum, magnesium, nylon, POM, and fiberglass were used due to weight saving and the non- magnetizable property. The structural weight corresponding to 15 % of the starting weight.
• Thermal Control System: Passive temperature control by means of suitable surface coatings, insulation and selection of appropriate materials.
• Orbit and attitude control: the end of the spin stabilization - the third high school accelerates the payload, after a successful burn out the second high school, at 150 1/min and then led the third acceleration phase ( injection into the transfer orbit to the Moon ) from. After the third upper stage burned out the speed was reduced to 100 1/min and reached after the deployment of the solar cells and the magnetometer about 27 1/min.
• Drive system: solid engine with APCP as fuel which has a specific impulse ( in vacuum) of 275 s delivered.
• Power supply: Four Solar Panels with a corresponding battery and Lade-/Entladeregulierungssystem. The DC / DC converter set voltages of 12, 20 and 28 V is available. The solar cells yielded a maximum of 66 W, with a maximum consumption of 52 W occurred.
• Telemetry and Data System: Various encoder for the experiments and instruments, transmitters and antenna system.

Findings

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

The probe was in addition to the measurement of the magnetosphere also data concerning the abundant protons, solar plasma, etc. to record and thereby extend the findings to the near-Earth environment.

Note

Differences in Orbit parameter specification on the part of NASA to other sources this can be seen due to perturbations on the part of the moon in the variation. This interference led to the perigee between 32000-200000 km, the apogee between 400,000-600,000 km and the inclination between 5-50 ° fluctuated. The differences between the stated mass of 212 kg, and 57.1 kg could not be identified, it seems likely that a quotation of the fuel masses. Also, there are differences in the indication of the error of the rocket stage ( 2nd or 3rd level), so that a capture by the moon's gravity field could not be done. Since there is no precise information is provided, which is started with Delta rocket Explorer 33 (Explorer 29 with a Delta E) is a statement in this respect is not possible.

The AMIP -D ( Anchored Interplanetary Monitoring Platform) should have a moon orbit with the parameters originally: reach lunar apogee of 6440 km, Lunar perigee of 1,288 km and a lunar inclination of 175 °.