Positional observations of satellites provide the basis to determine their orbits, and to study their optical characteristics. The latter provide the basis for the accurate brightness predictions that we have come to expect from our favourite prediction software or service.
Positional observations are analysed using computer programs, so observers need a systematic and accurate reporting format, ideally one that can be read by both humans and machines. The U.K. format is one of several that meet this need.
The following description has been adapted from the Satellite Observers Manual, compiled and edited by Howard Miles, and published by the British Astronomical Association.
Column number: 00000000011111111112222222222333333333344444444445555555555666666666677777777778 12345678901234567890123456789012345678901234567890123456789012345678901234567890 Example: YYLLLPPssssyymmddHHMMSSssssTttttSfHHMMmmmm+DDMMmmmMmmmE bbbfffSSSssO 9701201201803101520195542 01 12172038 +15585 1 5 +6 +8 190R Cols 01-07: Object's International Designation. Cols 01-02: year of launch Cols 03-05: sequential number of the launch in the year. Cols 06-07: piece from the launch, e.g. piece A denoted as 01 If object is unknown, enter 9900000. Cols 08-11: Observing Site Number. Cols 12-17: UTC Date of Observation, in YYMMDD format Cols 18-27: UTC Time of Observation, in HHMMSSssss format. Leave insignificant trailing zeros blank Cols 28-32: Time Accuracy, in seconds. Format is Ttttt, with decimal point implied after the first numeral. Col 33: Time Standard Code. Code 1: radio time signal, e.g. MSF. DIZ, WWV 2: U.K. Post Office Speaking Clock 3: B.B.C. time pips Col 34: Position Format Code. To allow for user preference, three RA/DEC and three AZ/EL formats are provided. The six positional formats are: Column 3333344444444445 5678901234567890 Code 1: RA/DEC = HHMMSSss+DDMMSSs 2: RA/DEC = HHMMmmmm+DDMMmmm 3: RA/DEC = HHMMmmmm+DDddddd 4: AZ/EL = DDDMMSSs DDMMSSs (elevation corrected for refraction) 5: AZ/EL = DDDMMmmm DDMMmmm (elevation corrected for refraction) 6: AZ/EL = DDDddddd DDddddd (elevation corrected for refraction) 7: AZ/EL = DDDMMSSs DDMMSSs (elevation not corrected for refraction) 8: AZ/EL = DDDMMmmm DDMMmmm (elevation not corrected for refraction) 9: AZ/EL = DDDddddd DDddddd (elevation not corrected for refraction) Cols 35-42: Observed Right Ascension or Azimuth, formatted per code in Col 34 Cols 43-50: Observed Declination or Elevation, formatted per code in Col 34 Cols 51-54: Position Accuracy. Units and format depend upon position code: Codes 1 and 4: seconds of arc, SSSs 2 and 5: minutes of arc, MMmm 3 and 6: degrees of arc, Dddd Col 55: Epoch of star chart used to determine position Code 1: 1855 2: 1875 3: 1900 4: 1950 5: 2000 6: 2050 0: any other date, which should be sent separately Cols 56-63: Range. Does not apply to visual observations. Units are km. Format is NNNNNnnn Visual observers should leave this field blank. Cols 64-68: Range Accuracy. Does not apply to visual observations. Units are km. Format is NNnnn Visual observers should leave this field blank. Cols 69-71: Brightest Visual Magnitude This is the brightest stellar magnitude attained by the satellite during the period of one minute centred on the time of the observation. It is entered as a 3 digit number, in one of the following forms: (1) if the satellite is brighter than magnitude +9.9 Column 69 is entered + or - Columns 70 and 71 state the numerical value, formatted as Mm (2) if the satellite is fainter than magnitude +9.9 The sign is omitted, and the numerical format is MMm Cols 72-74: Faintest Visual Magnitude Format is the same as for Brightest Visual Magnitude. (1) if the magnitude is constant, leave these columns blank (2) if the satellite becomes invisible, enter INV (3) if the faintest magnitude is not noted, leave these columns blank. There will be no confusion with a steady magnitude because of the entry in column 80. Cols 75-79: Flash Period Time in seconds between successive maxima, formatted as SSSss Col 80: Remarks. Code S: steady magnitude I: irregular brightness variations R: regular brightness variations F: flashing with constant flash period X: flashing with irregular flash period E: unusually faint because of eclipse exit/entrance Leave blank if not noted.
Links to: The VSO Home Page, Positional Measurements, Position Formats.