Vela 4A and Vela 4B are two spin-stabilized satellites which comprised the fourth launch in a series of six Vela launches. The orbits of the two satellites on each launch were basically circular at about 17 earth radii and spaced 180 deg apart. Their objectives were to study x-rays, gamma-rays, EUV, magnetic fields, and particles over a wide range of energies from solar wind to cosmic ray as the satellites passed through interplanetary space, the bow shock, magentosheath and magnetotail. Vela 4A operated well from launch unitl August 1, 1972, when tracking operations ceased.



X-Ray/Charged Particle
No Information

Gamma-Ray/Charged Particle
No Information

Neutron Detectors
The neutron detector was designed to monitor neutron signals from nuclear explosions in space and to establish background characteristics for neutron detectors exposed to neutrons and showers produced in the spacecraft by cosmic rays. The detector used a large polyethylene moderator to thermalize incident neutrons, the thermal neutrons were detected in two helium 3-filled proportional counters. Each counter had its own power supply and amplifier to afford greater reliability. Neutrons in the approximate range 1 - 100 MeV were counted and read out each second. The detector also reacted to (but did not distinguish) protons greater than 25 MeV in energy, thus it provided a simple indication of solar proton activity. The experiment worked well over the period of major data coverage.

Solar Wind Experiment
Four thin window Geiger-Mueller counters and one electrostatic analyzer - electron multiplier were used to study the solar wind and low energy electrons in interplanetary space and the magnetotail. The Geiger-Mueller counters measured the flux and angular distribution of electrons greater than 45 KeV. This experiment was active as of January 15, 1970. The electrostatic analyzer-electron multiplier unit was not working.

X-Ray Scintillation Counter
Cesium iodide detectors were used to monitor the quiescent solar x-ray flux and the x-ray flux from solar flares. One detector was used to study the integrated proton flux between 3 and 100 MeV. The experiment was active as of January 15, 1970

Solid State Detector
The purpose of this experiment was to study the intensity, spatial distribution, time variations, and energy spectra of the electrons in the transition region and in the tail of the earth's magnetosphere. The sensor consisted of a gold surface-barrier semiconductor detector. This detector was shielded from sunlight by two layers of nickel foil. The energy loss in these foils by electrons with energy greater than about 40 Kev was almost negligible. The instrument responded to electrons between 30 and 700 KeV and protons between 180 and 570 KeV. The energy spectrum was measured in steps by successive stepping of a pulse height analyzer giving seven points on the integral energy spectrum. Electrons and protons could be distinguished by comparision of this detector and the Geiger-Mueller experiment (NSSDC 67-040A-07) count rates. This experiment worked well over the period of major data coverage of the satellite.

X-Ray GM Tube + Scintillator
No information available.

Energetic Particle Solid State Telescope
Four semiconductor particle detectors, a photomultiplier tube, and a guard scintillator (for eliminating false pulses) in a telescopic arrangement with an angular view of 30 deg were used to study the directional intensity of protons betwee 0.5 and 100 MeV and alpha particles between 12 and 400 MeV. The experiment was active as of January 15, 1970.

EUV Detector
No information available.

Launch-Orbit Information

Launch Date: 1967-04-28
Launch Vehicle: Titan III-C
Launch Site: Cape Canaveral, United States
Mass: 231.0 kg