PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "S. Jeffers, 2005-01-21" RECORD_TYPE = STREAM RELEASE_ID = 0001 REVISION_ID = 0000 OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "MEX" INSTRUMENT_ID = "ASPERA-3" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = " ANALYZER OF SPACE PLASMA AND ENERGETIC ATOMS (3RD VERSION)" INSTRUMENT_TYPE = {"ELECTRON SPECTROMETER", "ION MASS SPECTROMETER", "NEUTRAL PARTICLE IMAGER", "NEUTRAL PARTICLE DETECTOR"} INSTRUMENT_DESC = " Instrument Overview =================== This is the ASPERA-3 (Analyzer of Space Plasmas and Energetic Atoms - 3rd version) instrument description. Analyzer of Space Plasmas and Energetic Atoms, 3rd version (ASPERA-3) ---------------------------------------------------------------------- Abstract. The general scientific objective of the ASPERA-3 experiment is to study the solar wind-atmosphere interaction and characterize the plasma and neutral gas environment in the near-Mars space through energetic neutral atom (ENA) imaging and local charged particle measurements. The studies to be performed address the fundamental question: How strongly do the interplanetary plasma and electromagnetic fields affect the Martian atmosphere? This question is directly related to the problem of Martian dehydration. The ASPERA-3 instrument comprises four sensors; two ENA sensors, electron and ion spectrometers. The Neutral Particle Imager (NPI) provides measurements of the integral ENA flux (0.1 -60 keV) with no mass and energy resolution but high angular resolution. The Neutral Particle Detector (NPD) provides measurements of the ENA flux, resolving velocity (0.1 -10 keV) and mass (H and O) with a coarse angular resolution. The electron spectrometer (ELS) is a standard top-hat electrostatic analyzer in a very compact design. These three sensors are located on a scanning platform providing a 4pi coverage (maximum possible). The instrument also contains an ion mass composition sensor, IMA (Ion Mass Analyzer). Mechanically, IMA is a separate unit connected by a cable to the ASPERA-3 main unit. IMA provides ion measurements in the energy range 0.01 - 40 keV/q for the main ion components H+, H2+, He+, O+, with 20-80 amu/q. Neutral Particle Imager (NPI) ----------------------------- The Neutral Particle Imager (NPI) provides measurements of the integral ENA flux with no mass and energy resolution but with 5 deg x 11 deg angular resolution. The intrinsic field of view is 9 deg x 344 deg. The sensor utilizes a graphite surface to suppress the UV background. ENAs incident on the surface at a grazing angle of 20 deg are reflected and/or cause ion sputtering. An MCP stack detects the reflected particles and sputtered fragments with a discrete anode. Neutral Particle Detector (NPD) ----------------------------- The Neutral Particle Detector (NPD) provides measurements of the ENA differential flux over the energy range 100 eV - 10 keV resolving H and O with a coarse 5 deg x 30 deg angular resolution. The sensor consists of two identical detectors each with a 9 deg x 90 deg intrinsic field of view. The measurement technique is based on a principle similar to NPI. ENAs incident on a surface at a grazing angle of 15 deg are reflected and cause secondary electron emission. The secondary electrons are transported to an MCP assembly, which gives the START signal. The reflected ENAs hit the second surface and again produce the secondary electrons used to generate the STOP signal. The time-of-flight (TOF) electronics give the ENA velocity. The pulse-height distribution analysis of the STOP signals is used to provide a rough determination of the ENA mass. Electron Spectrometer (ELS) --------------------------- The ELectron Spectrometer (ELS) provides electron measurements in the energy range 0.01 - 20 keV. The intrinsic field of view is 10 deg x 360 deg. The 360 deg aperture is divided into 16 sectors. The sensor is a standard top-hat electrostatic analyzer in a very compact design. Ion Mass Analyzer (IMA) ----------------------- The Ion Mass Analyzer (IMA) is a separate unit connected by a cable to the ASPERA-3 experiment. IMA provides ion measurements in the energy range 0.01 - 40 keV/q for the main ion components H+, H2+, He+, O+, and for the group of molecular ions 20 < M/q < ~80. IMA has a 4.6 deg x 360 deg field of view. Electrostatic sweeping performs elevation (+/- 45 deg) coverage. The IMA sensor is a spherical electrostatic analyzer followed by a circular magnetic separating section. A large diameter MCP with a discrete anode images the matrix azimuth x mass. Scientific Objectives ===================== The ASPERA-3 experiment fulfills the Mars Express mission objective of studying the interaction of the atmosphere with the interplanetary medium by: * Remote measurements of energetic neutral atoms (ENA) in order to (a) investigate the interaction between the solar wind and Martian atmosphere, (b) characterize quantitatively the impact of plasma processes on the atmospheric evolution, and (c) obtain the global plasma and neutral gas distributions in the near-Mars environment. * in situ measurements of ions and electrons in order to (a) complement the ENA images (electrons and multiply-charged ions cannot be imaged) (b) to study local characteristics of plasma (dynamics and fine structure of boundaries), and (c) provide undisturbed solar wind parameters necessary for interpretation of ENA images. The scientific objectives of the ASPERA-3 experiment are: 1) Scientific objective: Determine the instantaneous global distributions of plasma and neutral gas near Mars Associated measurements: ENAs originating from the shocked solar wind Measurement requirements: Measure the ENA flux in the energy range tens eV - few keV with 4pi coverage. ENA flux > 10**4/(cm**2-s-keV) Measure the upstream solar wind parameters 2) Scientific objective: Study plasma induced atmospheric escape Associated measurements: ENAs originating from the inside of the magnetosphere Measurement requirements: Mass resolving (H / O) ENA measurements in the energy range up to tens keV. ENA flux > 10**3/(cm**2-s-keV) 3) Scientific objective: Investigate the modification of the atmosphere through ion bombardment Associated measurements: ENA albedo Measurement requirements: Mass resolving (H / O) ENA measurements in the energy range down to tens eV from nadir direction. ENA flux > 10**6/(cm**2-s-keV) 4) Scientific objective: Investigate the energy deposition from the solar wind to the ionosphere Associated measurements: Precipitating ENAs Measurement requirements: ENA measurements in the energy range tens eV - few keV. ENA flux > 10**4/(cm**2-s-keV) 5) Scientific objective: Search for the solar wind-Phobos interactions Associated measurements: ENAs originating from Phobos Measurement requirements: ENA measurements in the energy range tens eV - few keV with 4pi coverage. ENA flux > 10**4/(cm**2-s-keV) 6) Scientific objective: Define the local characteristics of the main plasma regions Associated measurements: Ions and electron measurements of hot plasma Measurement requirements: Ion and electron measurements in the energy range few eV - tens keV with 4pi coverage. Calibration =========== Calibration of the ASPERA-3 sensors can be divided up in: 1. Characterization, tests and selection of detectors (MCPs and secondary emitting surfaces). 2. Characterization and final calibration of the integrated sensor units. 3. Functional tests of the sensors in the fully mounted (flight) configuration. All sensor units were fully calibrated, and some preliminary functional tests were made in the fully mounted, flight, configuration in June 2002. The final functional tests were successfully carried out during the retrieval period 18 November - 9 December 2002. The Neutral Particle Imager, NPI, was calibrated in Nov-Dec 2001 at the IRF ion source in Kiruna. The sensitivity of the instrument and the characterization of the acceptance field of view were obtained using ions (e.g. N+, H2O+, and H+). The ion deflector properties versus energy were calibrated for various deflector voltages. The integral efficiency of the secondary surface were found to range between 2% and 24% (MCP bias dependent). Azimuthal field-of-view slightly broader than nominal (13.5 deg). NPI-calibration performance as expectated. The ideal NPI field-of-view, 4pi, is coeverd in half a scan of the scanning platform. The Neutral Particle Detector, NPD, is a completely new design using secondary emitting surfaces and a geomtry that has not been flown before. NPD therefore underwent extensive characterisation tests and calibrations during the spring of 2002. The results of the calibrations at the IRF calibration facility in Kiruna were very successful, the NPD performance surpassing expectations. NPD is even more sensitive than expected. The mass and energy resolving capability of the instrument were as expected in the energy range ~1 - 10 keV. The NPD field-of-view, 2pi, is covered after a scan of the scanning platform. The Electron Spectrometer unit, ELS, was calibrated at MSSL in London, fall 2001. The energy resolution was found to be better than expected, which is an advantage for studying the narrow electron peaks expected as a result of the solar impact on the ionosphere and upper atmosphere. The geometric factor is a factor of five less than nominal, but the loss of sensitivity is, for this mission, considered to be well compensated by the improved energy resolution of ELS. Calibrations and tests are considered to be successful. IMA was successfully calibrated January to March, 2002. Performance largely as expected, except that the upper energy limit was lowered from 40 keV to 30 keV. Mass resolution, an energy and angular characteristics also as expected. Operation of ASPERA-3 ===================== The ASPERA-3 experiment contains four sensor units and the scanner. Each sensor unit measures different components of the near-Mars plasma and can be operated in different modes. To handle available power and telemetry resource requirements in the most efficient way and to inhibit too large number of individual modes, there are eight basic TM modes (macro modes): (1) OFF mode, (2) Safe mode, (3) Housekeeping mode, (4) Calibration mode, (5) Low mode, (6) Normal mode, (7) High mode, and (8) Burst mode. (1) OFF mode. The instrument is off although the external heaters are on and controlled by the instrument termistors. (2) Safe mode. At experiment power switch on, the instrument enters to a safe mode. In the safe mode the software is run in PROM although the software allows command execution, housekeeping TM generation, RAM dumping and jumping to the RAM code. The instrument also enters to the safe mode in the following cases: * the checksum of the RAM code fails * watch dog is not reset The safe mode is a fully operational mode, and the instrument is listening for other commands. (3) Housekeeping mode. In this mode none of the ASPERA-3 sensors are taking scientific data and the DPU delivers housekeeping data to OBDH. This mode is to monitor the instrument status. (4) Calibration mode. In this mode each of the different sensors is switched on individually for check-out and in-flight calibration purposes. (5-8) Low, Normal, High, Burst modes. These modes are for the scientific data taking. The modes differ from each other in the total amount of data produced and the structure of TM packages although individual settings defining the sensor configurations might be the same for different modes. The choice of the instrument operational mode for each phase of the mission is due to available power and telemetry as well as scientific requirements. The scanning platform has three operational modes: scanning mode, stepping mode, and fixed position mode. In the scanning mode, the platform performs scans with three pre-selected speeds 32, 64, and 128 sec in one 0 deg - 180 deg scan. In the stepping mode the platform moves in steps through the angle defined by a command. The time the platform rests in each position is also commanded. In the fixed position mode the platform moves to a commandable position from 0 deg to 180 deg and rests there until the scanner mode changes. All four ASPERA-3 sensors, ELS, NPI, NPD1 and NPD2, IMA, can be run independently although the individual sensor bit rates are set by a macro command. The raw data are compressed by integration over time, energy, azimuth, mass as well as using log-compression of 16-bit words to 8-bit words, masking, and look-up tables (NPD). The processed and formatted data are loss-less compressed by the USES algorithm (Universal Source Encoding for Space, CCSDS 111.0-W-2). Principal Investigator ====================== PI: Prof. Rickard Lundin Co-PI: Dr. Stas Barabash Both at Swedish Institute of Space Physics (IRF), Kiruna, Sweden" END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = BARABASHETAL2004 END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END