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THEMIS INSTRUMENT TRAINING ESA. Overview. Introduction ESA stands for Electrostatic Analyzer. It contains two detectors, one for measuring ions, one for electrons. It measures low energy particles up to 30keV. The ESA has flown on many missions including FAST. ESA Operation.
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Overview • Introduction • ESA stands for Electrostatic Analyzer. • It contains two detectors, one for measuring ions, one for electrons. It measures low energy particles up to 30keV. • The ESA has flown on many missions including FAST.
ESA Operation Particles enter the aperature and depending on their energy and the sweep voltage either travel between the two hemispheres and are counted or hit the sides and are discarded. The mircochannel plates detect the particles and produce a pulse which is counted.
ESA ITOS Page ESA current is about 40mA on power on. When it is running the HV the current doubles. Gain setting is usually 0xA0. Although this may change during the mission. The lower the number the lower the threshold for a valid count. ESA Pulser is used to simulate particles during I&T and for early commissioning but will not be used during the normal mission. HV settings. More on separate slide. ESA Cover will be opened early on in the mission once the spacecraft has out gassed sufficiently.
ESA Telemetry • ESA produces 4 types of data • APID 453 with the SST is moment data. Computed by the ETC Actel, this gives low resolution data of velocity, density and distribution of particles. • APID 455 and 458 are the reduced distribution functions. Enabled during Slow and Fast Survey, they are compressed time distributions of particle count at different angles. • APID 454 and 457 are the full distribution functions. Enabled during Slow and Fast Survey, they contain the full count of particles at different angles. • APID 456 and 459 are burst distributions. Just like the full distributions but at a higher resolution.
ESA Commands • ESA has an initialization script that is run on power up. Until then the actels are not in a defined state and there is the possibilty of damage to the instrument if the registers are not set correctly. The IESAICT command sends the default of startup commands stored in the IDPU. • ESA Cover opening requires the SMA supply from the IDPU. IACTSELECT command chooses the main or redundant cover. IACTTIME the duration of the pulse to actuator the SMA wire. IACTFIRE turns on the voltage to open the cover. The spacecraft 28V actuator supply needs to be on for the cover to be opened.
ESA HV The ESA requires four sets of high voltage supplies. Two that supply the hemispheric guiding plates and two supplies for the microchannel plate sensors. These supplies can only operate in a vacuum as in air or low vacuum they can arch and cause damage to the instrument and the power supply. It is also important that the spacecraft is out gassed sufficiently after launch. To enable the supplies the IESAHVENA1 and IESAHVENA2 commands need to be sent with the correct codes. The supplies are brought up in steps to verify proper functionality and to prevent high voltage arching. The first time the supplies are brought up on orbit it will be done during passes and slowly. Once confidence in the instrument and the procedure has been gained it is likely to be more automated by FSW. HV supplies need to be turned off for thruster firings.
