Vanguard 3

Vanguard 3

Vanguard 3 satellite
Names	Vanguard Space Launch Vehicle-7 Vanguard-TV4BU
Mission type	Earth science
Operator	Naval Research Laboratory
Harvard designation	1959 Eta 1
COSPAR ID	1959-007A
SATCATno.	00020
Mission duration	90 days (planned) 64 years, 9 months and 21 days (in orbit)
Spacecraft properties
Spacecraft	Vanguard 3C
Spacecraft type	Vanguard
Manufacturer	Naval Research Laboratory
Launch mass	42.9 kg (95 lb)
Dimensions	50.8 cm (20.0 in) diameter
Start of mission
Launch date	18 September 1959, 05:20:07GMT
Rocket	Vanguard SLV-7
Launch site	Cape Canaveral,LC-18A
Contractor	Glenn L. Martin Company
End of mission
Last contact	11 December 1959
Decay date	2259 (estimated) ~ 300 years orbital lifetime
Orbital parameters
Reference system	Geocentric orbit
Regime	Medium Earth orbit
Perigee altitude	512 km (318 mi)
Apogee altitude	3,750 km (2,330 mi)
Inclination	33.35°
Period	130.0 minutes
Instruments
Proton Precessional Magnetometer Micrometeorite Detectors Satellite Drag Atmospheric Density X-Ray Experiment
Project Vanguard

Vanguard 3(Harvard designation:1959 Eta 1) is a scientific satellite that was launched into Earth orbit by theVanguard SLV-7on 18 September 1959, the third successful Vanguard launch out ofeleven attempts.Vanguard rocket:Vanguard Satellite Launch Vehicle-7(SLV-7) was an unusedVanguard TV-4BU(TV-4BU=Test Vehicle-Four BackUp) rocket, updated to the final production Satellite Launch Vehicle (SLV).

Project Vanguardwas a program managed by theUnited StatesNaval Research Laboratory(NRL), and designed and built by theGlenn L. Martin Company(nowLockheed Martin), which intended to launch the first artificialsatelliteintoEarthorbitusing aVanguard rocket.as thelaunch vehiclefromCape Canaveral,Florida.Vanguard 3 was an important part of theSpace Racebetween the U.S. and theSoviet Union.

Previous satellites

Before the 18 September 1959 successful launch of the satellite that became known as Vanguard 3, two other satellites that bore the name "Vanguard 3" were launched, but both launches ended in failures and the satellites did not reach orbit. The failed satellites were:

• Vanguard 3A,launched 13 April 1959 on a Vanguard SLV-5 rocket,
• Vanguard 3B,launched 22 June 1959 on a Vanguard SLV-6 rocket.

The successful satellite that became known as the Vanguard 3 was known asVanguard 3Cbefore launch.

Spacecraft

The Vanguard 3 satellite was a 50.8 cm (20.0 in) diameter sphere with a 66 cm (26 in) conical boom on top. The lower three-fourths of the sphere wassilicon monoxide-coatedmagnesiumand the upper fourth and the conical extension were made offiberglass(glass fiber phenolic resin). Mass of the satellite was approximately 23.7 kg (52 lb), the total mass of the orbiting spacecraft with the 19.2 kg (42 lb) third stage casing attached was 42.9 kg (95 lb).

Power was provided by specially built Yardley Silvercels (AgZn chemical batteries) with non-magnetic lugs, designed to last approximately 3 months. The batteries were held in a pressurized can mounted in the lower two-thirds of the sphere. In its top center, the can also contained a smaller cylinder, which held the electronics for the X-ray, peak memory, temperature measurements, micrometeorite detector, and data encoder, above which was the 30mW,108.00MHzMinitrackbeacon transmitter. Another cylinder, mounted on top of the pressurized compartment, held the magnetometer instrumentation package, associated electronics, the command receiver and 80 mW, 108.03 MHz transmitter plus electronics providing bursttelemetryfor the magnetometer. Atape recorderwas used to store data for playback during ground station passes. Four spring loaded aerials extended from the equator of the sphere at 90° intervals. A smallsolar cellandcadmium sulfide cellwere also mounted on the sphere wall near the equator. The magnetometer sensor head was mounted at the end of the conical boom. The sphere was spin-stabilized and hadpassive thermal control.It had no engines for thrust orattitude control.

Launch

Vanguard 3 satellite sketch

Launch of Vanguard 3 on Vanguard SLV-7 rocket

Vanguard 3 was launched at 05:20:07GMT(12:20:07 a.m.EST) on 18 September 1959 from theEastern Test Rangeof theAtlantic Missile RangeatCape Canaveralinto ageocentric orbit.The satellite was then injected at 05:29:49 GMT into a 33.35°inclinationEarth orbit with aperigeealtitude of 512 km (318 mi),apogeeof 3,750 km (2,330 mi), and anorbital periodof 130.0 minutes. The third stage was purposely left attached to the satellite, in order to produce a long tumble period, to avoid corrections to the magnetometer that would be necessary with a rapidly rotating satellite. Perigee remained on the night side of Earth throughout the mission. All experiments functioned normally and the batteries lasted for 84 days, until 11 December 1959, at which time all communication with the spacecraft ceased. It was still tracked optically withtelescopesfor the atmospheric drag experiment.

Mission objectives

The objectives of the flight were to measure theEarth's magnetic field,the solarX-rayradiation and its effects on theatmosphere of Earth,and the near-Earthmicrometeoroidenvironment.Instrumentationincluded aproton magnetometer,X-ray ionization chambers, and various micrometeoroid detectors. The spacecraft was a 50.8 cm (20.0 in) of diametermagnesiumsphere. Themagnetometerwas housed in afiberglass/phenolic resinconical tube attached to the sphere. The data obtained provided a comprehensive survey of the Earth's magnetic field over the area covered, defined the lower edge of theVan Allen radiation belt,and provided a count of micrometeoroid impacts.

Mission results

Proton Precessional Magnetometer

This experiment had a proton precessional magnetometer to measure theEarth's magnetic fieldat altitudes ranging from 514 km (319 mi) to 3,714 km (2,308 mi) and at latitudes between ± 33.4°. The measurements were made on command as the spacecraft passed sevenMinitrackstations inNorthandSouth Americaand one each inAustraliaandSouth Africa.When switched on by command, the polarization coil around the proton sample (normal hexane) was turned on for 2 seconds followed by a 2 seconds readout of the precession signal. Several readings were taken during each pass over a station. The experiment worked well during its 84 days 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, Maryland, 1962, The overall accuracy of the field measurements was approximately 10nT(gammas).

X-Ray Experiment

The objective of this experiment was to measure the X-ray emission from theSunand its effects on theAtmosphere of Earth.The detectors were two identical ionization chambers sensitive to X-ray wavelengths produced in solar flares (2 to 8Å,or 200 to 800 pm). The ionization chambers were located 120° apart in the equatorial plane of the satellite and received a maximum signal when an ion chamber tube "looked" toward the Sun. The instrumentation were designed to measure the 2 to 8 Å (200 to 800 pm) X-ray flux and record the peak solar flare intensity by means of a peak-reading memory device, during the daylight portion of each orbit.However, due to the overwhelming background radiation of theVan Allen Belts,its sensors were saturated, and no useful information on solar X-rays was gathered.

Micrometeorite Detector

This experiment contained two sealed pressure zones, extending along the interior walls of the satellite, which were designed to record the impact ofmicrometeoriteslarge enough to pierce the satellite shell. These pressure zones were partial vacuums, each at a different pressure, and were protected by 0.66 mmmagnesiumwalls that presented an exposed surface area of 0.162 m²,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 byspace dust,micrometeorites,and other particles was recorded by threechromium-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, acadmium sulfidecell protected by an opaque covering ofaluminized PET film,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. Fourbarium titanate-typemicrophonesrecorded 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 hours interval from 16 to 18 November 1959, almost certainly due to the Earth's annual passage through debris from cometTempel-Tuttle,which results in theLeonids meteor showerwhich peaks on the 17 November 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 ofaltitude,latitude,season,andsolar activity.As the spacecraft continuously orbited, it would lag its predicted positions slightly, accumulating greater and greater delay due to drag of the residual atmosphere. By measuring the rate and timing of orbital shifts, the relevant atmosphere's parameters could be back-calculated knowing the body's drag properties. It was determined that atmospheric pressures, and thus drag and orbital decay, were higher than anticipated, as Earth's upper atmosphere tapered into space gradually.

This experiment was very much planned prior to launch. Initial Naval Research Laboratory proposals forProject Vanguardincluded conical satellite bodies; this eliminated the need for a separate fairing and ejection mechanisms, and their associated weight and failure modes. Radio tracking would gather data and establish a position. Early in the program, optical tracking (with aBaker-Nunn cameranetwork andhuman spotters) was added. A panel of scientists proposed changing the design to spheres, at least 50.8 cm (20.0 in) in diameter and hopefully 76.2 cm (30.0 in). A sphere would have a constant optical reflection, and constantcoefficient of drag,based on size alone, while a cone would vary with orientation.James Van Allenproposed acylinder,which eventually flew (Explorer 1). The Project Vanguard finally accepted 16 cm (6.3 in) and 50.8 cm satellites.

Post mission

After the scientific mission ended with data transmission ceasing on 11 December 1959, after 84 days of operation, Vanguard 3 and two pieces of the upper stage of the rocket used to launch the satellite becamederelictobjects.Vanguard 3 remains in orbit.The pieces of the upper stage re-entered the atmosphere on 3 April 2014 and 4 February 2015.AsVanguard 1,Vanguard 2,and Vanguard 3 are still orbiting with their drag properties essentially unchanged, they form a baseline data set on theatmosphere of Earththat is over 60 years old and continuing. Vanguard 3 has an expected lifetime of 300 years.