PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2009-11-27 JK: Update PVV 3.5.1 2010-04-21 JK: Fixed non ascii symbols 2016-10-27 PN: Fixed spelling 2017-06-29 PN: Fix energy range & Crew 2017-10-06 PN: Add PIU explanation 2018-01-19 PN: Fix energy range 2018-08-13 PN: Fix spelling " RECORD_TYPE = "STREAM" OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = RO INSTRUMENT_ID = "RPCICA" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = " ROSETTA PLASMA CONSORTIUM - ION COMPOSITION ANALYSER" INSTRUMENT_TYPE = "PLASMA INSTRUMENT" INSTRUMENT_DESC = " Instrument Overview =================== The Ion Composition Analyzer (ICA) is part of the Rosetta Plasma Consortium(RPC). ICA is designed to measure the three-dimensional distribution function of positive ions in order to study the interaction between the solar wind and cometary particles. The instrument has a mass resolution high enough to resolve the major species such as protons, helium, oxygen, molecular ions, and heavy ions characteristic of dusty plasma regions. ICA consists of an electrostatic acceptance angle filter, an electrostatic energy filter, and a magnetic momentum filter. Particles are detected using large diameter (100 mm) microchannel plates and a two-dimensional anode system. ICA has its own processor for data reduction / compression and formatting. The energy range of the instrument is from a few eV to 40 keV and an angular field-of-view of 360 deg times 90 deg is achieved through electrostatic deflection of incoming particles. The ICA instrument is based on the design of three earlier versions of this type of instrument. Those are the TICS instrument flown on the Swedish-German research satellite Freja which was operated between 1992-1996, the IMIS instrument which was part of the ASPERA-C experiment on the ill-fated Mars-96 mission, and the IMI instrument on the Japanese Nozomi mission to Mars. The instrument also has heritage from the ASPERA experiment flown on the Soviet spacecraft Phobos-2 to Mars. Furthermore an almost identical mass resolving ion spectrometer has been flown on the Mars Express mission, the IMA sensor of the ASPERA-3 instrument. One more copy, only slightly modified, is part of the ASPERA-4 instrument on Venus Express. RPC-ICA Characteristics ============================ Quantity Range Energy: Range a few eV to 40 keV Resolution Delta E/E$=0.07 Scan: 32 (solar wind) 96 (otherwise) Angle: Range (FOV) 90 x 360 degrees Resolution 5.0 x 22.5 degrees (16 elevation steps x 16 sectors) Temporal resolution: 2D distribution 4 s (12 s full energy range) 3D distribution 64 s (192 s full energy range) Geometric factor per 22.5 degree sector 6 10^{-4} cm^2 sr per 360 degree sector 1 10^{-2} cm^2 sr RPC-ICA Electronics =================== The ICA electronics can be divided into two main groups, high voltage power supplies for biasing of the various electrostatic filters and the MCP assembly, and digital electronics to handle the instrument operations. The high voltage supplies are laid out on two round boards in the cylindrical sensor part of the instrument. The high voltages are achieved by transforming an input voltage of 25 V to approximately 500 V, and subsequent chains of diode-capacitor voltage multipliers. ICA has two separate high voltage power supplies. One supply is dedicated to keeping the front side of the MCP biased to approximately -3 kV, while the other one supplies all other high voltages as fixed raw voltages. These raw voltages are then regulated by the use of high voltage opto-couplers. The electrostatic entrance filter can be stepped between +/-2.5 kV to an accuracy of 1.2 V using a 12-bit D/A-converter and the electrostatic energy filter is stepped between 0 and -4.5 kV also using a 12-bit D/A-converter and a high voltage opto-coupler. A high accuracy at low voltage settings is achieved by fixing the -4.5 kV supply at a voltage of about -100 V, and using a -11.25 V supply with a 12-bit D/A-converter connected to the outer ESA hemisphere to step the lower energy range. The post-acceleration voltage is also taken from the raw -4.5 kV voltage and set to the desired voltage using an opto-coupler. The digital electronics performs the following main functions: a) Reading data from the double-buffered sensor memory to the CPU and processing the data. b) Feeding the IEEE 1355 serial interface to the PIU, Plasma Interface Unit, with processed and formatted data. c) Receiving commands on the serial interface from the PIU. d) Controlling the high voltage power supply settings and monitoring voltages and temperatures. The digital electronics are built around an MA37150 processor. The on-board software runs from a 1 Mbit large bit-error corrected RAM. Flight software is stored both in 256 kbit PROM and in 4 Mbit EEPROM to enable patching of the software. An 8 Mbit memory is used both as working area for the CPU, and as a buffer for formatted data to be sent to the PIU. Data is transmitted to and from the PIU via a IEEE 1355 serial interface. ICA On-board data reduction ============================ Every sample period (approx. 125 ms), the ICA sensor produces a mass-angle-count matrix of the size 32 x 16 x 16 bits, for a total of 8192 bits per sample or 64 kbits per second. To reduce this large amount of data to the bit rates allocated to ICA (5, 100 and 1000 bits/s), the on-board CPU performs both data reduction and data compression. The basic measurement cycle consists of performing 16 energy sweeps at different settings of the acceptance angle filter, in order to step through the full field of view of the instrument. The energy sweep contains either 32 or 96 steps. A full 96 energy step measurement cycle is completed in 192s. The data is first reduced from a 16-bit representation to 8-bits using a logarithmic compression. Directions shadowed by the spacecraft are masked out to avoid sending invalid data. Options are available to mask out certain mass-channels which show large noise levels as well as certain acceptance angles which cannot be reached for certain energy levels due to finite resolution of the digital-to-analog converters controlling the energy-acceptance filter, see CALIB directory. Depending on the selected mode, the data is then reduced by different methods. Basically, the following two methods are used: a) The 32 mass channels are grouped together based on calibration data, and the sum of the grouped mass channels (representing a certain ion such as H+ or a certain ion mass range) is transmitted instead of individual mass channels. This will be referred to as mass-lookup tables and is used when the number of transmitted mass channels is less than 8. For 8 and 16 mass channels a simple integration of neighboring mass channels is used. b) Summation of angular bins, both the 16 stepped elevation angle and the 16 sector directions. The reduced data is finally compressed with a loss-less compression algorithm based on the Rice method. This compression reduces the data with approximately a factor of 5. Due to the data compression, the output data packets have variable length, and are buffered until enough compressed and time-stamped packets are available to fill a fixed length packet transmitted to the PIU. The buffer is also used to allow for higher than average production of data for some time. If data is coming in to the buffer faster than it is being removed by the TM stream an overflow will occur and data will be lost. The instrument can automatically adjust the reduction so that it fits the current efficiency of the compression. As an adjustable high and low ''watermark'' in the buffer is exceeded, the data reduction is changed accordingly. Mode description ================= ICA has in principle only one scientific mode. It measures 32 mass channels from 16 different sectors for 96 different energy intervals. The different science modes differ only in how much they reduce the data in order to fit a certain telemetry rate. The science modes are: ID Name MSPO Minimum spectra only MSIS Minimum, selected ion species MEXM Minimum, energy mass matrix NRM Normal mode, intermediate resolution HAR High angular resolution EXM High mass resolution For the end user, the used mode will be evident from the resolution of the data. Within each of the NRM, HAR and EXM modes there exist 8 sub-modes with different degree of binning of the data. HAR and EXM are intended for burst mode and differ in their strategy for reduction of the data. EXM keeps high mass resolution as far as possible, whereas HAR reduces mass resolution and preserves spatial resolution if the available telemetry is not enough to keep the current resolution of the data. NRM is intended for Normal mode telemetry and the minimum modes are intended for minimum telemetry rate. ICA field-of-view ================= The field-of-view is described in the EAICD document found in the DOCUMENT directory of this data set. A figure can also be found in the GEOMETRY directory, named ICALOCATION.JPG. ICA is located on the spacecraft +Z side, looking out over the edge on the + Y side. Its primary field-of view is the spacecraft x-z plane. The elevation scan can bring in particles from approximately +/- 45 degrees from this plane. For some angles of arrival the spacecraft will obstruct the field-of-view. This happens for sectors 10-15 and sector 0, for elevation index values 0 to 7. Output data =========== The output is energy spectrograms for certain mass channels and directions. The mass channels corresponds to physical locations on the detector plate, and calibration results must be used to determine which mass channels corresponds to a certain ion species or range of ion species. The data is obtained from 16 sectors looking in different directions and 16 different elevation angles out of the detector plane. The RPC ICA-CREW ================ PI: Hans Nilsson TM: Kjell Lundin (retired) Instrument: Olle Norberg, R. Lundin, S. Barabash, Kjell Lundin, Hans Borg Development: P. Riihelae On-board S/W: Hans Borg EGSE S/W: Hans Borg Archive S/W: Peje Nilsson Co-Is: S. Barabash A. Fedorov J.-A. Sauvaud H. Koskinen E. Kallio J. L. Burch References H. Nilsson, R. Lundin, K. Lundin, S. Barabash, H. Borg, O. Norberg, A. Fedorov, J.-A. Sauvaud, H. Koskinen, E. Kallio, P. Riihelae and J. L. Burch RPC-ICA: The Ion Composition Analyzer of the Rosetta Plasma Consortium, Space Science Reviews, doi:10.1007/s11214-006-9031-z, 2006" END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "NILSSONETAL2006" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END