1.2 mg/cm2 mica window about in diameter and weighing about . It detected soft x-rays efficiently and ultraviolet inefficiently, and was previously used in Injun 1, Explorer 12 and Explorer 14. It was able to detect protons above 500 keV in energy and electrons above 35 keV. The length of the basic telemetry frame was 887.04 seconds. During each frame, the counting rate of the detector was sampled twice at intervals separated by 37 seconds. The first sampling was the number of counts during an interval of 9.60 seconds (known as the 'long gate'); the second was the number of counts during an interval of 0.827 seconds (known as the 'short gate'). The long gate accumulator overflowed on the 256th count and the short gate accumulator overflowed on the 65,536th count. The maximum counting rate of the tube was 50,000 per second. A cosmic dust detector to measure the flux of cosmic dust particles in space. A solar plasma spectrometer to measure the spectrum of low-energy positively charged particles from the Sun, i.e. the solar wind. The magnetometer was attached to the top of the mast below the omnidirectional antenna. Particle detectors were mounted halfway up the mast, along with the cosmic ray detector. The cosmic dust detector and solar plasma spectrometer were attached to the top edges of the spacecraft base. The microwave radiometer, the infrared radiometer and the radiometer reference horns were rigidly mounted to a diameter parabolic radiometer antenna mounted near the bottom of the mast. All instruments were operated throughout the cruise and encounter modes except the radiometers, which were only used in the immediate vicinity of Venus. In addition to these scientific instruments, Mariner 2 had a data conditioning system (DCS) and a scientific power switching (SPS) unit. The DCS was a solid-state electronic system designed to gather information from the scientific instruments on board the spacecraft. It had four basic functions: analog-to-digital conversion, digital-to-digital conversion, sampling and instrument-calibration timing, and planetary acquisition. The SPS unit was designed to perform the following three functions: control of the application of AC power to appropriate portions of the science subsystem, application of power to the radiometers and removal of power from the cruise experiments during radiometer calibration periods, and control of the speed and direction of the radiometer scans. The DCS sent signals to the SPS unit to perform the latter two functions. Not included on any