PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 20061030, K. ALTWEGG Initial Version; 20200523 RChen/EN work around catalog ingest" RECORD_TYPE = STREAM OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "GIO" INSTRUMENT_ID = "NMS" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "NEUTRAL MASS SPECTROMETER" INSTRUMENT_TYPE = "MASS SPECTROMETER" INSTRUMENT_DESC = "Giotto Neutral Mass Spectrometer NMS Bern, 09.03. 2006 K. Altwegg Introduction ============ The Neutral Mass Spectrometer (NMS) was one out of ten scientific instruments on board of Giotto. Its primary objective was the determination of the chemical composition of gases and ions, the elemental abundances and isotopic ratios in the coma of comet P/Halley. The NMS sensor box contains two independent analyzers: A double-focussing mass spectrometer using a magnet as momentum filter (M-analyzer) and an electrostatic energy analyzer (E-analyzer) with second order angular focussing. The M-analyzer covers the mass range from 1 to 37 amu/e with a half peak width of 0.5 amu/e at the 0.01 level. In the neutral mode the E-analyzer observes the energy band from 200 to 2150 eV sampled in three steps. For thermal particles these energies correspond to a mass scale from 8 to 86 amu/e. In the ion mode the energy band of the E analyzer extends from 20 to 1420 e V, i.e. from 1 to 56 amu/e. List of NMS Investigators ========================= D. Krankowsky, Universitaet Germany, Heidelberg, PI P. Laemmerzahl, Max-Planck-Institut fur Kernphysik, Germany, Co-I J.-J. Berthelier, IPSL, St. Maur, France, Co-I P. Eberhardt, Universitaet Bern, Switzerland, Co-I J.H. Hoffmann, University of Texas, Dallas, Co-I R.R. Hodges Jr, University of Texas, Dallas, Co-I Short Instrument Description ============================ A complete description of the instrument can be found in Krankowsky et al. (1981) [KRANKOWSKYETAL1981]. Details on the data analysis can be found in Meier, 1992 [MEIER1992]. Other references include: [KRANKOWSKYETAL1986A], [WOWERIES1989], [DOLDER1986], [MEIER1988], [MEIER1992], [MEIER&EBERHARDT1993], [MEIERETAL1993], [MEIERETAL1994], and [REBER1997]. NMS consists of two independent analyzers in the same box sharing part of the digital electronics: a double-focussing Herzog- Matauch type mass spectrometer (M-analyzer) and an electrostatic energy analyzer (E-analyzer) with 2nd order angular focusing The mass range of the M-analyzer covers the range from u/e to 37 amu/e. The mass resolution at the 0.01-level is 0.5 amu/e. The E- analyzer is similar to the M-analyzer except that it contains no sector magnet. The detector of the E-analyzer has only half the active area as the M-analyzer. Seen from the NMS, all particles stream with the same constant velocity and therefore mass-dependent energy into the two entrances of the instrument. The E-analyzer therefore serves also as mass analyzer as long as the temperature of the gas is small compared to the relative velocity between spacecraft and gas. The E-analyzer covers in three steps the energy band between 200 eV and 2150 eV in the neutral mode and in two steps from 20 eV to 1420 eV in the ion mode. For cold particles this corresponds to a mass range from 8 to 86 u/e (Neutral mode), respectively 1 to 56 u/e (Ion mode). A mixture of gas and dust and ions enters the instrument with the velocity of 68 km/s. The collimator protrudes the dust protection shield of the spacecraft. It limits the field of view to 14 degrees relative to the ram direction in elevation and azimuth. The instrument consists of an ion source part, an analyzer part and the detector setup. Each of these parts contributes to the calibration factors to be used when analyzing the data. Entrance slit and ion source: ----------------------------- The entrance slit of the ion sourced has a size of 0.36 x 5.0 mm2. In the neutral mode the gas is ionized in the ion source block by electron bombardment. The electrons are generated by a hot filament. The electron energy is 18 eV in the LeV-Mode or 90 eV in the HeV- Mode. Electrical and magnetic analyzer: --------------------------------- The electrostatic field is made by a parallel plate analyzer which separates the ions according to their energies. The voltage applied is 31650 V/m (Toggle 0) or 34210 V/m (Toggle 1). The toggle mode shifts the recorded spectra by app. 2 mass units to compensate for bad pixels on the detector. A grid shields the magnet from the electrical field. The sector magnet has a gap of 5 mm and a field strength of 0.7 Tesla. Detector unit: -------------- The M-detector consists of four microchannel plates (MCPs) followed by self-scanning arrays of electron collectors (SSACs). The MCPs are placed end to end in the focal plane of the M analyzer. By altering the high voltage (MHV) across the MCPs (fifteen gain steps (GS), the detector gain (gain = number of collected electrons on the SSACs / number of incident ions) could be changed by more than six orders of magnitude. The heaviest ions fall onto detector number 1, the lightest on detector number 4. The area of each MCP is 25.4x15 mm2. Their thickness is 2 mm. The electrons are collected by a SSACs-Plate consisting of 64 semiconductor stripes (pixels, 0.4 mm wide and 5 mm high) which gives a total of 256 pixels. The accumulated charge is read out every 62.96 ms and is digitalized by a 12 bit ADC. Depending on the mode 7 to 18 read-out cycles are added to one spectrum. Measurements spanning 22.67 s are combined in one telemetry format and down linked. " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "KRANKOWSKYETAL1981" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "KRANKOWSKYETAL1986A" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "MEIER1992" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "MEIER&EBERHARDT1993" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "MEIERETAL1993" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "MEIERETAL1994" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "WOWERIES1989" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "DOLDER1986" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "MEIER1988" END_OBJECT = INSTRUMENT_REFERENCE_INFO OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "REBER1997" END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END