Data Set Summary ================ Data Set ID: ULY-J-COSPIN-AT-4-FLUX-256SEC-V1.0 Instrument: COSPIN Anisotropy Telescope (AT) Instrument P.I.: R. Bruce McKibben (COSPIN), Robert J. Hynds (AT) Data Supplier: Robert J. Hynds Data sampling rate: 256 seconds Data Set Start time: 1992-01-25T00:02:08.000Z Data Set Stop time: 1992-02-17T23:55:44.000Z Naming convention ----------------- Data files in this data set are named according to the convention: Tyyddd.TAB where yy = the last two digits of the year ('92' for 1992) ddd = the day of the year covered by the file Record format ------------- These files can be read according to the FORTRAN format statement: '(a24,16(1x,1pe10.3))' where 'a24' is the time stamp in PDS format: yyyy-mm-ddThh:mm:ss.sssZ. The individual elements of the time field can be read according to the statement: '(i4,4(1x,i2),1x,f6.3,1x)' year, month, day, hour, minute, seconds. thus a record may be alternatively be read according to the format: '(i4,4(1x,i2),1x,f6.3,1x,16(1x,1pe10.3))' Data column descriptions ------------------------ time a24 spacecraft event time fluxch1 1pe10.3 channel 1 spin-averaged flux fluxch2 1pe10.3 channel 2 spin-averaged flux fluxch3 1pe10.3 channel 3 spin-averaged flux fluxch4 1pe10.3 channel 4 spin-averaged flux fluxch5 1pe10.3 channel 5 spin-averaged flux fluxch10 1pe10.3 channel 10 spin-averaged flux fluxch11 1pe10.3 channel 11 spin-averaged flux fluxch12 1pe10.3 channel 12 spin-averaged flux fluxch7 -- 8 1pe10.3 flux data values from sectors 1-8 from channel 7 Missing data flag value ----------------------- Any data column whose value is -9.999e+10 is a missing data value. Data Description ================ The Imperial College Anisotropy Telescope ----------------------------------------- (Last updated: 17 March 1995) This document describes the Anisotropy Telescopes, the data they provide, and the format of the data files provided by Imperial College to the Ulysses Data System. NB. Please take careful note of the following points: (1) THE INFORMATION PROVIDED IN THIS FILE CORRECTS AND UPDATES INFORMATION PRESENTED IN [SIMPSONETAL1992A]. In particular, the Anisotropy Telescope pointing directions were given incorrectly in [SIMPSONETAL1992A], and the energy channel widths quoted there have since been updated. (2) See the Ulysses Data System guidelines for restrictions on the use of this data. 1. The Anisotropy Telescopes ---------------------------- The Anisotropy Telescope (AT) experiment is a two-telescope device. The telescopes are nominally identical with Telescope T1 pointing at 60 degrees to the spacecraft spin axis (i.e. in the Earthward looking hemisphere) and telescope T2 pointing at 145 degrees (i.e. in the anti-Earthward looking hemisphere). They have a full-cone opening aperture of 70 degrees and a geometric factor of 0.7 cm^2 sr. Together they provide 80% coverage of the full sky. The most significant gap in the coverage is a cone with a half angle of 25 degrees centered on the Earthward pointing line along the spacecraft spin-axis. There is also a 5 degree gap in coverage between the two telescopes. 2. The full AT Data set ----------------------- Spin-averaged and sectored data in a variety of energy channels is produced by the ATs, as follows: Channel Energy range Energy Range Sectored / number /MeV (protons) /MeV (alphas) Spin-averaged ----------------------------------------------------------------- 1 0.7 - 0.9 2.3 - 2.5 Spin-averaged 2 0.9 - 1.3 2.5 - 2.7 Spin-averaged 3 1.3 - 2.2 2.7 - 3.0 Spin-averaged 4 2.2 - 3.6 ----------- Spin-averaged 5 3.6 - 6.5 24.0 - 28.0 Spin-averaged 6 0.7 - 1.3 2.3 - 2.7 Sectored (8) 7 1.3 - 2.2 2.7 - 3.0 Sectored (8) 8 2.2 - 3.6 ----------- Sectored (8) 9 3.6 - 6.5 24.0 - 28.0 Sectored (8) 10 --------- 3.0 - 7.5 Spin-averaged 11 --------- 7.5 - 12.0 Spin-averaged 12 --------- 12.0 - 26.0 Spin-averaged 13 --------- 3.0 - 7.5 Sectored (4) ----------------------------------------------------------------- 3. AT data provided to the Ulysses Data System ---------------------------------------------- The AT data provided in these files is a subset of the total data set which is held at Imperial College. The format of these files is as follows: There is one data file per day. Each data file contains data records for every ten minute interval in the day, except during the Jupiter encounter (1992, days 25 to 48 inclusive) where data at 256s resolution is provided. Each record contains 21 fields of information, the first five being time-stamps referring to the centre time of the data contained in the remaining 16 fields. The definition of these fields, including their FORTRAN format, is given below. N.B. Fluxes quoted are from telescope T1, which points at 60 degrees to the spacecraft spin axis. -------------------------------------------------------------- Field Fortran Definition Format -------------------------------------------------------------- 1 a24 Time in PDS format: yyyy-mm-ddThh:mm:ss.sssZ 2 1pe10.3 Flux from channel 1 3 1pe10.3 Flux from channel 2 4 1pe10.3 Flux from channel 3 5 1pe10.3 Flux from channel 4 6 1pe10.3 Flux from channel 5 7 1pe10.3 Flux from channel 10 8 1pe10.3 Flux from channel 11 9 1pe10.3 Flux from channel 12 10 1pe10.3 Flux from channel 7, sector 1 11 1pe10.3 Flux from channel 7, sector 2 12 1pe10.3 Flux from channel 7, sector 3 13 1pe10.3 Flux from channel 7, sector 4 14 1pe10.3 Flux from channel 7, sector 5 15 1pe10.3 Flux from channel 7, sector 6 16 1pe10.3 Flux from channel 7, sector 7 17 1pe10.3 Flux from channel 7, sector 8 -------------------------------------------------------------- Each record is written using the FORTRAN format (i4,4(1x,i2),1x,f6.3,1x,16(1x,1pe10.3)) or (a24,16(1x,1pe10.3)) 3.1 Definition of flux ---------------------- in this table, flux means differential flux in units of (cm^2 sr s MeV)-1 (NB. per MeV, not per MeV per nucleon). The fluxes have been computed by dividing the observed count rates by the geometric factor and the energy channel width. The energy channel width depends on species. Where a channel is sensitive to alpha particles and protons (i.e., channels 1, 2, 3, 5, 6, 7 and 9), the proton width has been used since normally the alpha contribution is insignificant. However, sufficient information has been given above to reconstruct the channel count-rates if necessary. All AT channels exhibit a "background" which may originate from electronic noise or from activation of the material of the telescopes or of the spacecraft. These background fluxes have been subtracted from the data provided in these files. Channel 3 and channel 7 are the channels least affected by background and it is for this reason that channel 7 has been selected to provide the sectored data included in these files. The data have also been "despiked", although it is not guaranteed that all spikes have been removed. 3.2 Definition of sectors ------------------------- All sectored channels except channel 13 have eight 45 degree sectors. Channel 13 has only 4 sectors. Sector 1 of channel 13 is a 90 degree sector equivalent to sectors 1 & 2 of any of the other sectored channels. Similarly, sector 2 of channel 13 is equivalent to sectors 3 & 4 of any other sectored channel, etc. The sectoring scheme is defined relative to the "sun crossing line". The sun-crossing line is the line in the plane defined by the Sun, the Earth and Ulysses, which is perpendicular to the Ulysses-Earth line and which makes an angle of less than 90 degrees to the Ulysses-Sun line. For channels with 8 sectors, sector 1 is the 45 degree sector which starts from the sun-crossing line and extends in the sense of spacecraft rotation. Sector 2 begins at the angle that sector 1 ends and continues in the sense of spacecraft rotation, etc, continuing through to sector 8 which ends at the the sun-crossing line.