PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2004-11-21, SONC, initial release " RECORD_TYPE = STREAM OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "RL" INSTRUMENT_ID = "ROMAP" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "ROSETTA LANDER MAGNETOMETER AND PLASMA MONITOR" INSTRUMENT_TYPE = {"FLUXGATE MAGNETOMETER", "ELECTROSTATIC ANALYZER","FARADAY CUP"} INSTRUMENT_DESC = " Instrument Overview =================== The ROMAP sensors (fluxgate magnetometer, electrostatic analyser and Faraday cup) measure the magnetic field from 0 to 32Hz, ions up to 8.0 keV and electrons up to 4.2 keV. High integration level of sensors and electronics is the basic for a combined field/plasma measurement instrument with less than 1 Watt power consumption and 1 kg mass. Additional two pressure sensors are included in the ROMAP sensor arrangement. The sensors are moved from COSAC to ROMAP to optimise long term operation of pressure sensors. Data of both pressure sensors are transmitted within the housekeeping frame and are handled / archived as housekeeping values. Scientific Objectives ===================== Main scientific goals of ROMAP are (1) long term measurements on the surface to study the cometary activity as function of the distance from the Sun and (2) magnetic measurements during the descent phase of the Lander to investigate the structure of the remnant magnetization of the nucleus. Calibration =========== MAG : Data are precalibrated by nominal scaling. Offsets can not be corrected automatically. This will be done by sequence specific cal files (L3). Finally corrected data (includes the removal of spacecraft disturbances) are only available for selected data of scientific interest (L5). SPM : Instrument calibration will be done preliminary (L3) and finally for derived data products (L5). Operational Considerations ========================== Main measurement sequences are: - During Flybys - During Descent - On cometary Surface Common operation with Instruments generating magnetic interferences shall be avoided. Common operation with RPC-MAG onboard the orbiter is highly desirable Electronics =========== The ROMAP electronics consists of two boards placed inside the common electronics box. The central part of the near sensor electronics on the first board is a FPGA which controls AD and DA-converters. The 16-bit AD converters are digitising science and housekeeping data from all three sensors. Typical analogue parts of fluxgate magnetometers like filters or phase-sensitive integrators are substituted by fast digitalization of the sensor AC-signal and the following data processing in FPGA's (which overtakes the functions of the former analogue parts). In this way mass is saved without any loss of accuracy. The resolution is still restricted by sensor noise (less than 5pT/sqrt(Hz) at 1Hz), not by electronics. Compensation fields for the magnetometer and high voltage steps for electrostatic analyser and Faraday cup are controlled via DA-converters (dashed lines). The near sensor electronics is developed by Magson GmbH Berlin The high voltage generator (developed by the KFKI) is in a separate shielded box on the front panel of the common electronics box. The controller is located on the second ROMAP board. It controls MAG and SPM, stores their data output and implements the interface to the Lander Command and Data Management System (CDMS). It triggers the measurement cycle of the magnetometer, implements the digital magnetometer algorithm, controls the magnetometer feedback and generates data frames. For the SPM sensors the controller has implemented the counting logic for electrons and ions, samples Faraday cup data, generates SPM data frames, controls the high voltage parameters (energy, elevation), controls the channeltron HV-supply and computes the plasma parameters. In the parameter mode only the sums of the rows and columns of the sampled ion and ion-current arrays are transmitted. The controller is based on a RTX2010. Address decoder, reset logic, clock generators, control signals generator, watchdog logic and CDMS interface are integrated within a FPGA. Hard- and software are developed by the IWF Graz. Sensor / Sensor Location ======================== The magnetometer sensor consists of two ringcores (crossed in to each other) as well as pick-up coils and Helmholtz coils for each sensor axis. The coil system design without mechanical support allows the compensation of the external field on the ringcore position with high homogeneity and low weight (the overall sensor weight is 30g). Dynamic feedback fields as well as offset fields up to 2000nT can be generated in order to compensate Lander and/or Orbiter DC stray fields. The main part of the SPM-sensor is a hemispherical electrostatic analyzer with two channeltrons (CEM's) for ions measurement and one for electrons measurement. The entry of the ion channels is equipped with deflection plates to realize the spatial resolution. Despite the small size of the sensor, the sensitivity and resolution of the instrument are high and its field of view wide (appr. 100 degree). The E/q-range extends from 0 to 8 kV. Using CEMs in counting mode the electrostatic analyzer measures electron and ion distribution in a wide energy range. Hemisherical deflection plates analyze the energy in 32 or 64 steps. All major plasma parameters as bulk velocity, density and isotropic temperature of protons and electrons can be derived. A retarding-grid Faraday cup sensor is implemented to measure currents due to fluxes of low energy charged particles on a collector plate. The Faraday cup measures the 'reduced' velocity distribution of the plasma due to its inherent integration over velocities contained in a plane of differential thickness perpendicular to the axis of the sensor. The combined magnetometer / SPM sensor is mounted on a 60 cm boom which is fixed with a hinge on the upper edge of the Lander structure and with a launch lock on the Lander balcony. After opening the launch lock, the boom will be deployed by two springs inside the hinge. Two pressure sensors are selected to cover the whole pressure range from 10^-8 mbar to 10 mbar. For the range from 10^-8 mbar to 10^-3 mbar an ionising system (Penning) is deployed while for the range from 10^-3 mbar to 10 mbar a heat conduction sensor (Minipirani) is available. Operational Modes ================= ROMAP can be basically operated in 3 modes: - Slow Mode - Fast Mode - Surface Mode Subsystems ========== The sub-systems are described in Auster et al, 2005. Measured Parameters =================== Magnetic field; resolution 10 pT Electrons: 0.35 ... 4200 eV Ions: 40 ... 8000 eV Pressure; 10^-8 mbar to 10 mbar. " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID ="AUSTERETAL2007" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END