PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 2006-01-27, L.Kamp, Created. 2006-06-16, L.Kamp, Revised per comments from 2006.06.12 DAWG. 2006-11-27, L.Kamp, Revised per comments from SBN. 2007-10-18, Maud Barthelemy, 70 char line length. " RECORD_TYPE = "STREAM" OBJECT = INSTRUMENT INSTRUMENT_HOST_ID = "RO" INSTRUMENT_ID = "MIRO" OBJECT = INSTRUMENT_INFORMATION INSTRUMENT_NAME = "MICROWAVE INSTRUMENT FOR THE ROSETTA ORBITER" INSTRUMENT_TYPE = {"RADIOMETER","SPECTROMETER"} INSTRUMENT_DESC = " Instrument Overview =================== The MIRO instrument will provide both very sensitive continuum capability for temperature determination and extremely high- resolution spectroscopy for observation of molecular species. The MIRO instrument consists of two heterodyne radiometers, one at millimeter wavelengths (1.3 mm) and one at submillimeter wavelengths (0.5 mm). The millimeter and the sub-millmeter radiometers have continuum bandwidths of 0.5 GHz and 1.0 GHz respectively in addition, the submillimeter receiver has a total spectroscopic bandwidth of 180 MHz and a spectral resolution of 44 kHz. In the spectroscopic mode, 4096 channels, each having a bandwidth of 44 kHz, are observed simultaneously. Instrument Summary ================== The performance parameters that govern the MIRO instrument design include system sensitivity, spatial resolution, radiometric accuracy (both absolute and relative), beam pattern and pointing accuracy, together with the mass, power, volume envelope, and environmental conditions available within the spacecraft. The MIRO instrument performance characteristics are summarised in Table below. Equipment Property MM-Wave SubMM-Wave Telescope Primary Diameter 30 cm 30 cm Primary F/D 1 1 Sidelobes -30 dB -30 dB Spatial Resolution 24 arcmin 8 arcmin Footprint (at 2 km) ~15 m ~5 m Spectral Freq Band 188.5-191.5GHz 547.5-580.5GHz Performance 1st IF Bandwidth 550MHz 11GHz 1st IF Freq Rng 1-1.5GHz 5.5-16.5GHz Spectral Resolution n/a 44 kHz Spectral Rng per line n/a nominally 20 MHz Accuracy n/a 10 kHz Spectrometer Center Freq/Bandwidth n/a 1350/180 MHz Number of channels n/a 4096 Radiometric DSB Receiver Noise 800 K 3800 K Performance Temperature SSB Spectroscopic Sens (300 KHz, 2 min) relative n/a 2 Krms absolute n/a 3 Krms Continuum Sens (1 sec): relative 1 Krms 1 Krms absolute 3 Krms 3 Krms Data Rates Instantaneous Rate Continuum Mode <1 kbps Spectroscopic Mode 2 kbps On-board Storage 0.2 Gb (1) (1) One day's data volume, Mode 3, 100 Duty cycle, see Vol 6., Table 6.3.1-1) Abbreviations used in above: Freq = Frequency Rng = Range Sens = Sensitivity MIRO Data Modes =============== The MIRO instrument has 6 major modes of operation and data- taking that reflect operational combinations of its two continuum radiometers and the spectrometer, engineering mode, millimeter continuum mode, submillimeter continuum mode, dual continuum mode, CTS/submillimeter continuum mode, and CTS/dual continuum mode. In addition, a special mode has been designed for planetary and asteroid flybys. A number of data compression options are obtained in each mode by varying the data-taking rate (integration time per sample) and/or spectral resolution of the radiometers and spectrometer. The parameters for each mode are summarized below. For more details, see the MIRO User Manual (AD4 of the EAICD, RO-MIR-IF-0001_14), Volume 6.1. 1. Engineering Mode In engineering mode the MIRO software is collecting engineering data from 56 internal sensors. The sampling of these sensors is at a 5 Hz rate. All engineering measurements are 12-bit A/D converted values. The engineering mode telemetry is sent to the spacecraft in the form of a housekeeping telemetry packet. One engineering telemetry packet is typically generated every 11 seconds. 2. Millimeter Continuum Mode In millimeter continuum mode continuum data are collected from the millimeter radiometer at a 20 Hz. rate. All continuum data consist of 16-bit values. The millimeter continuum data are nominally packetized into science telemetry packets every 10 seconds. A 'summing value' parameter can cause the MIRO software to sum either 1, 2, 5, 10 or 20 separate continuum values prior to putting them into the telemetry packet. This feature can reduce the data rate to as little as one millimeter continuum packet every 200 seconds. 3. Submillimeter Continuum Mode Submillimeter continuum mode is identical to the millimeter continuum mode in data collection and packing, except that a different set of electronics is powered on. Millimeter and submillimeter continuum data are contained in separate science telemetry packets, identified by a field in the source data header. 4. Dual Continuum Mode In dual continuum mode the millimeter and submillimeter continuum are collected simultaneously. When running in dual continuumvmode, the summing value parameter mentioned earlier is applied to both sets of data, causing equal amounts of millimeter and submillimeter data to be generated. 5. CTS / Submillimeter Continuum Mode This mode adds the collection of chirp transform spectrometer (CTS) data. The CTS is programmed by the MIRO software to run for an initial sub-integration period of approximately 5 seconds. An internal LO frequency generator is then switched and another 5 second period is observed. These pairs of observations are repeated with the respective results being summed over time. Selectable integration periods are 30, 60, 90 and 120 seconds. The data from the two LO frequencies are then subtracted from each other to provide a single 4096-element difference spectrum. The 4096 data values can be further reduced by application of a smoothing function whereby data from several channels are combined and weighted to produce fewer final channels. Smoothing window sizes are 1, 5, 7 and 9 channels. A mask is applied to the CTS data and only 12 bits of each resulting measurement are returned. CTS data collection and the LO frequency switching is coordinated with the collection of continuum data. Exactly 100 continuum samples are taken during each CTS scan. Upon receipt of the data on the ground it is known at which LO frequency all of the continuum measurements were made at. If the CTS has just been powered on, an internal calibration of the CTS is performed. This consists of loading the 4 CTS sum of square tables with a linear ramping pattern. A 10,000 cycle integration is then performed and the resulting data read out. The data are then averaged to yield the mid-point of the table. The resulting mid-point values for each table are downlinked in telemetry packets for monitoring over time. 6. CTS / Dual Continuum Mode This is the same as the CTS / SMM continuum mode except that the millimeter data are also collected. 7. Asteroid Mode This special data-taking mode has been implemented for the asteroid and planetary encounters to enable MIRO to follow the rapid Doppler shift of spectral lines that may be visible. The primary characteristic of this mode is that LO frequency switching is turned off. The LO is set to either +5 MHz or - 5 MHz from the nominal frequency prior to the encounter. At the specified encounter time, the LO frequency is switched _ 5 Mhz (opposite from the first setting) from the nominal frequency. Continuum data are collected at 20 Hz. Each set of CTS data consists of a single 5-second integration with all 32 bits returned for each 4096 channels. " END_OBJECT = INSTRUMENT_INFORMATION OBJECT = INSTRUMENT_REFERENCE_INFO REFERENCE_KEY_ID = "GULKISETAL2007" /* MIRO Instrument Paper */ END_OBJECT = INSTRUMENT_REFERENCE_INFO END_OBJECT = INSTRUMENT END