PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2010-03-17, SONC, initial release 2015-01-31, PIship modified, new PI added P.Henri LPC2E/CNRS 2015- " RECORD_TYPE = STREAM OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = RO INSTRUMENT_ID = "RPCMIP" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "ROSETTA PLASMA CONSORTIUM - MUTUAL IMPEDANCE PROBE" /* RLC: _TYPE was MUTUAL IMPEDANCE PROBE */ INSTRUMENT_TYPE = "ELECTROSTATIC ANALYZER" INSTRUMENT_DESC = " Instrument Overview =================== MIP is composed of an electric antenna and a HF analyser. The MIP antenna comprises two receivers and two transmitters, supported by a conductive bar. This antenna is mounted on the upper boom of the spacecraft. Scientific Objectives ===================== The MIP instrument measures the electrical coupling between a transmitting antenna and a receiving antenna. The plasma density, temperature, and drift velocity are then identified from the features of the frequency response. In its passive mode, this instrument has also the capability of a plasma wave analyser. It is therefore used to detect the electric fields of electrostatic and electromagnetic waves. These waves are associated with the interaction of the solar wind, with the charged dust, and ionized outgassing products of the comet nucleus, as well as the impulsive signals generated by individual dust particles impacting the spacecraft surface. Calibration =========== MIP has no specific testing mode, it is nevertheless checked at each switching on command of the instrument in the first 32 s sequence called Control sequence. This Control sequence is sent with the science data, and contains : - one byte test with results of watchdogs and memory tests, - one loop Survey mode in which the transmission signal is directly connected to the receiving electronics, and - samples of the input FIFO. When a new command is sent to MIP, a Table sequence is generated. It is identical to the Control sequence, except for the byte concerning results of watchdogs and memory tests, which is replaced by a counter. Operational Considerations ========================== There is no operational constraints. The best results are obtained when the antenna is in front of the spacecraft, refer to its velocity vector. Detectors ========= The antenna comprises two receiving electrodes, 1 m apart, closely coupled with preamplifiers. Their sensitivity varies from 4 micro-Volt per square root Hz at 7 kHz, to 0.12 micro-Volt per square root Hz at 3.5 kHz. Electronics =========== The MIP electronics is based on : - a digital frequency synthesizer working from 7 kHz to 3.5 MHz, - one analogue acquisition channel followed by a 7.17 MHz sampling system, and - a data processor which delivers spectra computed by FFT. Filters ======= The bandwidth is limited from 1 kHz to 3.5 MHz by an antialiasing filter. Optics ====== Not applicable. Location ======== Not applicable. Operational Modes ================= The MIP instrument can be used in active mode, or in passive mode. In active mode the ambiant plasma is excited by one or two, among the three transmitters. There is three main active modes : - the Survey mode consists of a sweep over the frequency bandwidth which can be selected from 28 kHz to 3.5 MHz, - the Sweep mode is always triggered by a Survey mode, it allows us to scan a limited frequency bandwidth around the resonance with a better frequency resolution, - the LDL mode is used when the Debye length is over 20 cm. In this case the signal is transmitted by the LAP2 probe in the 7 - 168 kHz frequency bandwidth . In passive mode no signal is transmitted, it consists of a power spectrum over all the 7 kHz - 3.5 MHz frequency bandwidth . Subsystems ========== Not applicable. Measured Parameters =================== An alternating current, I, with a frequency lying in the frequency range that contains the plasma frequency resonance, is driven through a transmitting electrode. The induced difference in voltage, V, measured on open circuit between two receiving electrodes is fed into a high input impedance amplifier. The mutual impedance, Z, which is then computed onboard, is equal to the ratio of V to I. As Z depends essentially on the properties of the surrounding plasma, the frequency response of the mutual impedance probe may be used for plasma diagnosis. Due to the resistive, capacitive, and/or inductive nature of the plasma, the frequency response has got both real and imaginary components that provide valuable insights into the plasma characteristics. In the active mode, the electron density and temperature and the bulk velocity of the ionized outflowing atmosphere are determined from the shapes of the real and imaginary parts of the MIP frequency response. In the passive mode, when no current is injected through the transmitting electrode, the sensor is actually a receiving electric antenna. It detects natural waves, and impulsive signals due to the expanding plasma clouds generated by dust particles impacting the antenna and the spacecraft. RPC-MIP responsibilities ======================== PIship: Jean-Gabriel Trotignon LPC2E/CNRS 1996-2012 Jean-Pierre Lebreton LPC2E/CNRS 2012-2015 P.Henri LPC2E/CNRS 2015- Hardware and science operations management: Jean-Louis Michau LPC2E/CNRS 1996-2007 Xavier Vallieres LPC2E/CNRS 2008- RPC-MIP hardware and ground support equipment have been developed by four laboratories: - LPC2E/CNRS, for the flight electronics board and software - ESA/RSSD, for the RPC-MIP electrical antenna manufacturing and testing - FMI has partly provided the electrical ground support equipment - IRF-U contributes to the implementation of the Long Debye Length mode The overall responsibility is ensured by LPC2E/CNRS. " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "TROTIGNONETAL2007" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END