Vanguard 3
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| Missing image Vanguard_3.jpg Vanguard 3 | |
| Organization: | Department of the Navy |
| Major Contractors: | Naval Research Laboratory |
| Mission Type: | Earth Science |
| Satellite of: | Earth |
| Launch: | September 18, 1959 at 05:16:00 UTC |
| Launch Vehicle: | Vanguard rocket |
| Decay: | 300 year orbital lifetime |
| Mission Duration: | December 11, 1959 - 84 days |
| Mass: | 22.7 kg |
| NSSDC ID: | 1959-007A |
| Webpage: | NASA NSSDC Master Catalog (http://nssdc.gsfc.nasa.gov/database/MasterCatalog?sc=1959-007A) |
| Orbital elements | |
|---|---|
| Semimajor Axis: | 8,506.2 km |
| Eccentricity: | .189872 |
| Inclination: | 33.3° |
| Orbital Period: | 129.7 minutes |
| Apogee: | 3,744 km |
| Perigee: | 512 km |
| Orbits: | ~182,000 as of July 17, 2004 |
| Instruments | |
| Proton Precessional Magnetometer : | Measure the earth's magnetic field |
| Micrometeorite Detectors : | Record the impact of micrometeorites |
| Satellite Drag Atmospheric Density : | Determine upper atmospheric densities |
| X-Ray Experiment : | Measure the X-ray emission from the sun |
| Contents |
Mission Objectives
Vanguard 3 was launched by a Vanguard rocket from the Eastern Test Range into a geocentric orbit. The objectives of the flight were to measure the earth's magnetic field, the solar X-ray radiation and its effects on the earth's atmosphere, and the near-earth micrometeoroid environment. Instrumentation included a proton magnetometer, X-ray ionization chambers, and various micrometeoroid detectors. The spacecraft was a 50.8-cm-diameter magnesium sphere. The magnetometer was housed in a glass fiber phenolic resin conical tube attached to the sphere. Data transmission stopped on December 11, 1959, after 84 days of operation. The data obtained provided a comprehensive survey of the earth's magnetic field over the area covered, defined the lower edge of the Van Allen radiation belt, and provided a count of micrometeoroid impacts. Vanguard 3 has an expected orbital lifetime of 300 yr.
Mission Results
Proton Precessional Magnetometer
This experiment had a proton precessional magnetometer to measure the earth's magnetic field at altitudes ranging from 514 to 3714 km and at latitudes between plus or minus 33.4 deg. The measurements were made on command as the spacecraft passed seven minitrack stations in North and South America and one each in Australia and South Africa. When switched on by command, the polarization coil around the proton sample (normal hexane) was turned on for 2 s followed by a 2-s readout of the precession signal. Several readings were taken during each pass over a station. The experiment worked well during its 85-day active life, and approximately 4300 readings were recorded. The experiment is described in J. C. Cain et al., "Measurements of the geomagnetic field by the Vanguard 3 satellite," NASA TN D-1418, Goddard Space Flight Center, Greenbelt, Md., 1962. The overall accuracy of the field measurements was approximately 10 nT (gammas).
Micrometeorite Detector
This experiment contained two sealed pressure zones, extending along the interior walls of the satellite, which were designed to record the impact of micrometeorites large enough to pierce the satellite shell. These pressure zones were partial vacuums, each at a different pressure, and were protected by 0.66 mm magnesium walls that presented an exposed surface area of 0.162 m˛, which was 20% of the area of the shell. A puncture in the walls of either zone was detected by a differential pressure gauge mounted between them, and telemetered as a change in the length of one of the telemetry channels. Erosion of the satellite shell through bombardment by dust, micrometeorites, and other particles was recorded by three chromium-strip erosion gauges mounted on the satellite surface, and by a photosensitive detector. Electrical resistances of the gauges changed as their surfaces were changed by erosion. The photosensitive detector, a cadmium-sulfide cell protected by an opaque covering of MylarŽ plastic and deposited aluminium, also showed a resistance change as the covering was eroded or penetrated. Erosion measurements also were telemetered as channel lengths, which permitted estimates of the erosion rates. Four barium-titanate-type microphones recorded micrometeorite impacts on the satellite's surface. The microphone output was amplified, shaped, and fed into a magnetic counter unit, which provided continuously, in three-decimal digits, the cumulative count of impacts. The unit counted up to 1000 and then reset to zero. The satellite recorded 6600 micrometeorite impacts during 66 days of operation, of which 2800 occurred during a 70-h interval from November 16 to 18, 1959. No penetrations or fractures were recorded in the sensors of the surface penetration experiment. Because the erosion sensors were not disrupted, no definite results could be drawn from that experiment.
Satellite Drag Atmospheric Density
Because of its symmetrical shape, Vanguard 3 was selected by the experimenters for use in determining upper atmospheric densities as a function of altitude, latitude, season, and solar activity. This experiment was not planned prior to launch. Density values near perigee were deduced from sequential observations of the spacecraft position, using optical (Baker-Nunn camera network) and radio and/or radar tracking techniques. This experiment obtained reasonable density values. Vanguard 3 has an expected lifetime of 300 yr.
X-Ray Experiment
The objective of this experiment was to measure the X-ray emission from the sun and its effects on the earth's atmosphere. The detectors were two identical ionization chambers sensitive to X-ray wavelengths produced in solar flares (2 to 8 A). The ionization chambers were located 120 deg apart in the equatorial plane of the satellite and received a maximum signal when an ion chamber tube "looked" toward the sun. The instrumentation measured the 2- to 8-A X-ray flux, and recorded the peak solar flare intensity by means of a peak-reading memory device, during the daylight portion of each orbit.
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