Data Set Information
DATA_SET_NAME HUYGENS HASI MISSION RAW AND CALIBRATED DATA V1.1
DATA_SET_ID HP-SSA-HASI-2-3-4-MISSION-V1.1
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview: THe Huygens Atmospheric Instrument is one of the six experiment onboardthe Huygens probe. HASI is a muultisensor package designed to measurethe physical quantities characterizing Titan's atmosphere during entryand descent phase and at the surface. Science Objectives and Observational Strategy:HASI science objectives for the Huygens missione are to:- determine the atmospheric density, pressure and temperature profiles- Determine the atmospheric electric conductivity and charge carrier profiles- Investigate ionisation processes- Survey of wave elelctric fields, lightining and analyse the quasi-static electric fields leading to storm formation- Detect acoustic noise due to turbulence or storm- Characterise the roughness, mechanical and electric properties of the surface material, whatever its phase, solid or liquid These objectives are addressed at one location and time, but a veryhigh resolution ground thruth for the calibration of remote sensingobservations.The observational strategy for the Huygens probe is fixed by aprogrammed sequence, HASI observations, mode switching are organizedin a timeline triggered by events (e.g. T0 detection), time andaltitude information provided by Huygens CDMS via the DDBL (DataDistribution Broadcast Line). Parameters: HASI S/W provides two independent telemetry queues: one dedicated toeach Huygens Command and Data Management Unit (CDMU). HASI handles TMpackets queues by the internal operating system, that allocatedynamically the memory for the packets. The memory remains allocateduntil the tM packet is discarded from the queue (TM queue capabilityof about 130 packets).Few seconds (about 132 s) after HASI power ON HASI telemetry starts(both on CDMU-A and CDMU-B). Acquired data are transmitted redundanton both CDMUs (with the exception for PWA science data, same packetcontent is transmitted on both CDMU TM line, but only one chain isconsidered valid). Till TdataH (T0+2.5 min) HASI data are trasmitted,but remains stored in the memory. After TdataH (when the link betweenHuygens probe and Cassini should be safelly established, storedpackets are retransmitted as original).During entry phase, when HASI is the only operative instrument, inorder to cope with the higher CDMS polling rate also copies of thepackets stored in the TM queues are re-transmitted. HASI presents to the Huygens Probe Command and Data Management System(CDMS) about 8-9 TM packets for CDMS cycle (16 s).Each HASI telemetry packets is composed of a header containing packetidentification, sequence count and lenght. The first data containedin the packets data field corresponds to the time stamp relevant tothe HASI mission time when the first value has been measured. The timerelevant to the single values contained within the data field iscomputed according to their position (sensor sampling and packetfilling rate).Time relevant to each data value contained in thetelemetry packet is computed starting from the timestamp, according totheir position within the packets and from the sampling rate (constant). HASI marks each telemetry packets with a timestamp relevant to the DDB timewhen the first source data contained in the packet data field is created.Timestamp resolution is a BCP count (125 ms); the resolution on this timevalue is 1 LSB : 1ms. DATA: The HASI telemetry packets are filtered into data format relevant to thedifferent subsystem and operational mode. The raw binary data arereformatted into ASCII tables reporting as first column the relevantmission time. Structure of DATA Directory:HASI data are organized in different folders divited by subsystem.They are:ACC: Triaxial ACCelerometer subsystemTEM: TEMperature sensorsPPI: Pressure Profile InstrumentPWA: Permittivity, Wave and Altimetry packageHK: DPU (Data Processing Unit) housekeepingPROFILES: higher level products Parameter within data filename are indicative for:- sensor, data processing level, datatype, mission phase and/or mode. File naming convention: The data product file naming convention is as follows:HASI_L{data processing level}_{subsystem}{missionphase}_{datatype}.{ext}data processing level {2, 3, 4} according to CODMAC processing levelsubsystem {ACC, TEM, PPI, PWA, DPU}mission phase {E : entry , D : descent, S : surface} when applicablesensor data type {SERVO, SERVOSTD, SERVOT, PIEZO, PIEZOSTD, PIEZOT,PIEZOIMP}; {FINE1, COARSE1,...}; {NSA,HCA, HK, NSA11P, NSA13T, ...};{RP, AC_ELF, AC_VLF, ACU, LGH, MIP, RAU}extension {LBL : label, TAB : table} Ancillary Data: The time reference (mission time) is given by the Huygens timerprovided to the instrument in the Descent Data Broadcast (DDB) by theHuygens Command Data and Management System (CDMS).HASI receives a DDB information every 2 s and is synchronized every125 ms by the BCP (BroadCast Pulse) signal.In preT0 (entry phase), time is referenced to Huygens probe power on (S0);after entry time is referenced to T0 (arming time of the Descent DeviceDeployment System pyros).HASI marks each telemetry packets with a timestamp relevant to the DDB timewhen the first source data contained in the packet data field is created.Timestamp resolution is a BCP count (125 ms); the resolution on this timevalue is 1 LSB : 1ms.Conversion from DDB time (Mission Time) to UTC time will be provided byHPOC (Huygens Probe Operation center).Native time (enlapsed from T0) in s a sign '-' for preT0. Huygens Probe auxiliary data such as reference dimensions, mass, CoG,products of Inertia evolution, parachute characteristics and the Huygensaerodynamical database have been provided by the Project and are archivedwithin the Huygens HouseKeeping (HK) data set. Coordinate System: The reference system for HASI is the Huygens probe system axes.The official trajectory reconstruction is the result of a common effort,based a subset of Huygens experiments and housekeeping data, produced bythe Huygens Descent Trajectory Working Group (DTWG) and archived withinthe Huygens DTWG data set.Huygens reference system: Titan centric coordinates (as defined by DTWG). Software: HASI data files are tables of ASCII format fields for eachhousekeeping and science data elements. This simple conversion fromthe raw, binary EDR records involves no irreversible change or datareduction. As such, the level 2 data set represents an appropriateprimary archive of all of the raw HASI data delivered to the ground andthere is no expectation of any need for reprocessing to perform thisconversion in the future. Accordingly, the software used to read theHASI raw, binary files and create the higher level data is not archivedwith this data set.All the processing, transfer function and calibration applied to the rawdata are described in the subsystem Calibration reports contained in theCALIBRATION directory. Within this documents are also reported the errorbudget and measurement uncertainties.
DATA_SET_RELEASE_DATE 2006-10-12T00:00:00.000Z
START_TIME 2005-01-14T09:01:17.453Z
STOP_TIME 2005-01-14T12:10:20.828Z
MISSION_NAME CASSINI-HUYGENS
MISSION_START_DATE 1997-10-15T12:00:00.000Z
MISSION_STOP_DATE N/A (ongoing)
TARGET_NAME TITAN
TARGET_TYPE SATELLITE
INSTRUMENT_HOST_ID HP
INSTRUMENT_NAME HUYGENS ATMOSPHERIC STRUCTURE INSTRUMENT
INSTRUMENT_ID HASI
INSTRUMENT_TYPE ACCELEROMETER
NODE_NAME Planetary Atmospheres
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview: The HASI data set represents all HASI data from the Huygens probe missionat Titan as recovered from the Cassini Solid State Memory and Cassini-Huygens Project ground system.The multiple redundant data streams, downlinked have been checked andmerged to provide the most complete and correct sequence. Data Coverage and Quality: The HASI data set is organized into a separate data file for each sensorpackage as listed in the Data section under DATA_SET_DESC above.The overal data quality is very good. The loss of channel A resulted intothe loss of some PWA data that were not redundant (e.g. Relaxation probeand Radar). No data gaps caused by telemetry dropouts have been recorded. For higher level products some concerns are still open:- calibration for PWA data: only level 2 is provided in this dataset.- The Huygens DTWG trajectory is incoherent to the altitude profileretrieved from Huygens radar altimeter.Different approaches and methods applied to HASI data resulted in altitudeand velocity profiles showing discrepancy not consistent with uncertaintyrange relevant to models and measurements.The reason for this discrepancy is still under investigation.Future analysis could imply the need for reconsolidate the trajectory. DOCUMENTS: The DOCUMENT directory contains the files that provide documentation andsupplementary information to assist in understanding and using the dataproducts. DATASET VERSION:The data set id is HP-SSA-HASI-2-3-4-MISSION-V1.1. The file ERRATA.TXTexplains the differences with the previous archived data setHP-SSA-HASI-2-3-4-MISSION-V1.0. CALIBRATION Directory: This directory contains files providing the calibrationinformation of the HASI subsystems. HASI ACKNOWLEDGEMENT/CREDITS: The Cassini-Huygens mission is a cooperative project of NASA,the European Space Agency (ESA) and the Italian Space Agency(ASI). The Huygens Atmospheric Structure Instrument (HASI)onboard the Huygens probe is a multisensor package designedto measure the physical quantities characterizing Titan'satmosphere.Prof Marcello Fulchignoni is the HASI Principal Investigator.The HASI Project Office is at CISAS 'G. Colombo' of theUniversity of Padova (UPD), Italy and is coordinated by ASI'sObservation of the Universe Directorate. The Accelerometer (ACC) subsystem has been designed, developed,assembled and provided by the United Kingdom. The ACC team isbased at Planetary and Space Sciences Research Institute (PSSRI)of the Open University, UK. The Pressure Profile Instrument (PPI) subsystem has beendesigned, developed, assembled and tested by the FinnishMeteorological Institute (FMI), Helsinki, Finland. The Temperature sensors (TEM) have been designed, developed,assembled and tested by CISAS 'G. Colombo' of the Universityof Padova (UPD), Italy. The Permittivity, Wave and Altimetry (PWA) subsystem has beendesigned, developed and tested by a collaboration of institutes:the Research and Science Support Department (RSSD), ESTEC, ESA,the Institut fuer Weltraumforschung (IWF), Graz, Austria;the Laboratoire de Physique et Chimie de l'Environnement, (LPCE),CNRS - CNES, Orsay, France; the Instituto de Astrofisica deAndalucia (IAA-CSIC), Granada, Spain. The acoustic sensor is part of the Permittivity, Wave andAltimetry (PWA) subsystem and has been designed, developed andtested by the Space Research Institute (Institut fuerWeltraumforschung, IWF) of the Austrian Academy of Sciences, Graz,Austria. For more information on the HASI instrument, visithttp://cisas.unipd.it/hasi/ CREDITS:HASI_ACC ESA/ASI/UPD/OUHASI_TEM ESA/ASI/UPDHASI_PPI ESA/ASI/UPD/FMITRAJECTORY altitude and vertical profile ESA/ASI/UPD/OU/FMIHASI_PWA ESA/ASI/UPD/RSSD/CNR/IWF/IAA-CSIC Review: The Huygens data sets were reviewed in two steps: (1) a review of the Experimenter-to-archive-ICD, in 2004. (2) a review of the data sets, in 2006. Procedures and details of this process can be obtained from the ESA archive team: Olivier Witasse or Joe Zender ESA ESTEC Keplerlaan 1 2200 AG Noordwijk The Netherlands Olivier.Witasse@esa.int or Joe.Zender@esa.int This data set was reviewed by Ralph Lorenz and an anonymous reviewer.
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ABSTRACT_TEXT The Huygens Atmospheric Instrument is one of the six experiment onboard the Huygens probe. HASI is a muultisensor package designed to measure the physical quantities characterizing Titan's atmosphere during entry and descent phase and at the surface.
PRODUCER_FULL_NAME HASI_TEAM
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