AMPTE UKS/IRM General Caveats SJ Schwartz UK Coordinated Data Handling Facility for Solar Terrestrial Physics Queen Mary and Westfield College History ======= 4 March 1997 Draft Version 24 Nov 1999 Added Caveats re IRM Temperatures (IRM-PLA) and gaps (P3) The UK CDHF for STP is a joint QMW/RAL Project. Contents ======== Purpose Mission Constraints Prime Parameters Instrument Caveats UKS - IRM Orbit Files UKS Electrons UKS Ions - FTR UKS Ions - SW UKS Waves UKS Correlator UKS Missing Data Table IRM Plasma Purpose ======= This document describes known aspects or problems with the AMPTE UKS and IRM data held at and supplied by the UK CDHF. For more detailed information on specific instruments, prospective users are urged to contact the Principal Investigator(s) concerned. A full list of PIs, together with the rules regarding data access, use, and authority to publish, can be found in accompanying documents held at http://www.space-plasma.qmw.ac.uk/CDHF/ Mission Constraints =================== M1 AMPTE UKS coverage was limited to approximately one 5-hour contact period each day. UKS survived from launch until 15 January 1985. M2 Nearly all positional information, including the UKS/IRM separation vector, was generated from tracking data by G Spalding (RAL); the on-board ranging failed after one month. No formal assessment of the inter-satellite ranging errors is known. More details are given below in ORB- caveats. M3 UKS times are UT as stamped by the on-board clock. IRM times are UT at time of ground receipt. Thus for time-critical science, the IRM times need to be corrected by subtracting the light travel time from the spacecraft to the ground-station (at Weilheim in Germany apart special events requiring NASA DSN). For the transmission frequencies used, the vacuum light speed is appropriate. At apogee, this correction is more than a third of a second. There are no other known time delay. See P1 and P2 below for further caveats concerning Prime Parameter timings. Prime Parameters ================ P1 ALL IRM Prime Parameters were derived from spin-averaged moments. They were delivered to RAL on exact 5-second timetags for initial use within the GDF database system. This was accomplished by straightforward averaging of all (typically one!) data points within a given 5 second interval. Thus the IRM Prime Parameter timetags were effectively shifted by up to 2.5 seconds. There is no procedure to recover the actual times of the measurements without recourse to the original raw dataset. P2 The Prime Parameter holdings are a mixture of data originally held at the GDF at RAL, which worked to the convention that timetags represented START times, and newly deposited data which conforms with the Cluster specification of time-CENTRED tags. The following table records the situation with regard to particular files. The version number can be found at the end of the cdf file name, e.g., UK_PP_ELX_19840826_V01.cdf is a Version 1 file for UKS electron prime parameters for 26 August 1984. This file name is also held as a Global Attribute "Logical_file_id" and the version number as the Global Attribute "Data_version" within the CDF files. UKS Electrons V01 Start UKS Ion FTR V01 Start UKS Ion SW V01 Start UKS Magnetom. V01 Centre UKS AC Waves V01 Start UKS Wave Power V01 Start UKS Wave Spect. V01 Start UKS-IRM Orbit V01 Centre [tbc] IRM Auxiliary V01 Start IRM General V01 Start IRM Magnetom. V01 Start IRM Plasma V01 Start IRM Suleica V01 Start IRM Waves V01 Start P3 In some modes of operation, IRM plasma distributions were sampled with shifted phases in 4 successive spins with the result that there is no data for the 5th spin. This provides improved angular resolution, especially in the solar wind, if averaged over the 4 spins. Whether there is a data gap in the PP file depends on the timing of the spins (see P1 above). Instrument Caveats ================== UKS - IRM Orbit Files --------------------- Caveats and other information are also held at: http://sspg1.bnsc.rl.ac.uk/Share/AMPTE/orbit.htm and links therein. ORB-1 The UKS/IRM intersatellite ranging system (scalar) failed on 23 September 19984 after approximately one month of the mission. The vector ranging system was never operative. Most ranging data is therefore based on orbital parameters, whose errors are uncertain. The period 23 September - 21 November is particularly prone to errors, as after that time "beam swinging" techniques were introduced which resulted in better orbital parameter determination. ORB-2 Orbit fiels have been separated at boundaries corresponding to different orbital parameters. Merging two orbital files may then result in a small discontinuity around the merge time, which may need smoothing or filtering. UKS Electrons ------------- Caveats and other information are held at: http://sspg1.bnsc.rl.ac.uk/Share/AMPTE/electron.htm and links therein. UKS Ions - FTR -------------- UKS-FTR-1 V01 files contain data which has not been fully validated by the instrument team. Moreover, an error in data compression/ decompression tables has not yet been corrected, although this is believed to have negligible effect on the plasma moments. Nonetheless, would-be users are urged to contact the PI team at an early opportunity. UKS Ions - SW ------------- UKS-SW-1 See UKS-FTR-1 above. UKS Waves --------- UKS-W-1 The UKS wave antenna was a single 7m dipole. Corrections are necessary if amplitudes are required. UKS-W-2 Several spacecraft interference lines are present in the SFA data UKS-W-3 The Auto-correlator sometimes saturated due to the way the (Waves) Automatic Gain Control operated. UKS-W-4 There is an interference line in the ACC data at ~ 1.5kHz UKS-W-5 Some correlograms require "fixing" by the PI. UKS Correlator [Note, no correlator data is present in the current database] -------------- UKS Missing Data Table ---------------------- The following table gives an overview of days for which data is not present from one or more instruments in the UKS Prime Parameters but for which the UKS was in operation. Note that UKS did not operate on some days; these are indicated by DOY------------ below. [DOY = Day of Year; ELX = Electrons; ION = Ions; WAV = Waves; MAG = Magnetometer.] DOY ELX ION WAV MAG 84... 238 x x x 243 x 244 x 246 x 247--------------- 250--------------- 251 x 257 x x 259 x 260 x x x x 261--------------- 264 x 265 x 266--------------- 268 x x 269 x 270 x x 272 x 273 x x 274--------------- 275--------------- 279 x x x 281 x x x x 282 x x x x 287 x x x x 288 x 290 x 292 x 294 x 298--------------- 299 x 300--------------- 301 x x 307 x 308 x 311--------------- 313 x 314 x x x x 317 x 319 x 322--------------- 325 x 330 x 331 x 334 x 335--------------- 336 x 342 x 345 x 346 x 347 x 348--------------- 349 x 350 x 351 x 353 x 354 x x 355 x x 356 x 357 x 358 x x 359--------------- 360 x x 361--------------- 362 x 363 x 364 x 365 x x 85... 003 x 005 x 006--------------- 007 x 009 x 010 x x 011 x x 013 x x x 016 x x x x IRM PLA ------- IRM-PLA-1 Electron and ion temperatures deposited in the GDF at RAL were incorrectly stored there with units of 10**6K. V01 PP_PLA files repeat this UNITS information, with corresponding values for SI_conversion to Kelvin. However, this is incorrect. The correct entries should read: UNITS: "keV" SI_conversion: "1.16e7>K" for BOTH T_p%IR_PP_PLA and T_e%IR_PP_PLA End of AMPTE UKS IRM General Caveats File