Each PEACE Instrument has two sensors. These are both controlled by a Data Processing Unit (DPU). The DPU also collects measured data from the sensors, which it organises and condenses before passing on to the spacecraft data handling system for transmission to Earth.
Each Sensor consists of :
- a Top Hat Electrostatic Analyser which, at any one moment, only permits electrons of a narrow range of energies to pass through it and so reach the detector. A specialised High Voltage Generator is used to vary the voltage across the analyser hemispheres in a controlled manner, thereby varying the energy of admitted electrons, so that large range of energies are sampled in a short time. Tens of energy spectra are collected during each spacecraft spin.
- a Detector-Counter subsystem, which registers the arrival of electrons after they have successfully passed through the Analyser. It is also able to approximately determine their arrival direction. The subsystem contains a microchannel plate chevron pair (MCP), a discrete Anode, a Capacitor Board and an Amplifier Board. A second High Voltage Generator is used to operate the MCP.
- a Sensor Electronics Unit (SEU) which controls the detailed operation of the sensor, a motherboard and a box to house the electronics. The SEU is provided by the Norwegian Defence Research Establishment.
- The MCPs are supplied by Photonis. The procurement and initial characterisation of the MCPs is performed by the Space Science Department of the Rutherford Appleton Laboratory.
- The Capacitor Board, Amplifier Board and Motherboard are also provided by the Space Science Department of the Rutherford Appleton Laboratory. The MCP and Analyser High Voltage Generator Boards are also provided by the Rutherford Appleton Laboratory.
Data Processing Unit
The PEACE DPU interfaces with both the sensors and the spacecraft telemetry stream via T2 transputers. The Science Processor services the sensor interface and the and Interface Processor handles the spacecraft telemetry interface. The whole system is contolled by OCCAM software. This software calculates moments, spacecraft potential and pitch angle distributions onboard. More detailed 2D and 3D distributions may be telemetred whenever telemetry permits.
The hardware is built by a collaboration of
- The Mullard Space Science Laboratory, of University College London, University of London (Principal Investigator Team)
- The Rutherford Appleton Laboratory
The following UK companies have also contributed to the PEACE project in the hardware areas specified:
- Morgan Matroc Limited (anodes)
- Walton Plating Limited (hemisphere coating)
- Edwards Brothers (hemisphere manufacturing)