Event File Structure

11SEP22 Restructured web-page
Contents

Overview

An Event File is an editable text file containing a series of PARAMETER=VALUE statements providing sufficient time and location data to simulate an occultation event for the Cubemap Instrument Bypass module in order to generate L1B files.

The same Event File is used for both HIROS and HSDI.

Example: event.txt, which can be read with IDL function read_event.pro

File Structure

Parameter Value Definition Units Range
Mandatory Parameters
SATELLITE String Name of satellite, eg 'Cubemap 1'
ORBIT Long Orbit#, > 0
LAT_START Float Tangent Pt Latitude at Event Start deg N −90 : +90
LAT_END Float Tangent Pt Latitude at Event End deg N −90 : +90
LON_START Float Tangent Pt Longitude at Event Start deg E −180 : +180
LON_END Float Tangent Pt Longitude at Event End deg E −180 : +180
Either: specify external Observation List [4]
OBS_FILE String Name of Observation File eg 580_40_equi.txt
Or: create local Observation List from all the following [4]
JULIAN_DAY Long Julian Day#, eg 9132 (0=1Jan2000, 9132=1Jan2025) [5] > 0
MSC_START Long Event Start Time within day (UT) ms 0 : 86400000
MSC_END Long Event End Time within day (UT) ms 0 : 86400000
MSC_HSDI Long HSDI sampling interval eg 1000 (=1sec) [6] ms > 0
MSC_HIROS Long HIROS sampling interval eg 2000 (=2sec) [6] ms > 0
ALT_START Float Geometric Tangent Altitude at Event Start [7] eg 10.0 (for sunrise event) km > 0 expected
ALT_END Float Geometric Tangent Altitude at Event End [7] eg 60.0 (for sunrise event) km > 0 expected
RAD_CURVE Float Earth Radius of Curvature in line-of-sight, [8] eg 6378.0 km 6300.0 – 6400.0 expected

Notes

  1. Spaces are allowed either side of the PARAMETER or VALUE fields.

  2. Any part of a record following a '!' character is ignored, so this can be used to add comments. Empty records are also ignored.

  3. Strings are assumed to be separated by spaces, so use single or double quotes if the string VALUE includes any spaces, eg 'Cubemap 1'

  4. The list of tangent altitudes can either be read from a separate 'Observation List' file (OBS_FILE), or can be generated directly by specifying the start/end altitude and the sampling interval.

  5. This is a modified definition of Julian Day, commonly used by ESA. The formal definition, starting on 1 Jan 4713 BC, is used in the Observation List File. The IDL function read_event.pro includes the conversion to modified Julian Day.

  6. When creating a set of observations from the event file alone, it is possible to specify separate sampling rates for HIROS and HSDI.

  7. Sunrise/Sunset events are distinguished by the ALT_START altitude being lower/higher than ALT_END.

  8. RAD_CURVE, if present in the event file, will override the values in the OBS_FILE (eg useful for ensuring consistency with the single value used in the Scene Generator).

Document Changes

11SEP22 Web-page reformatted - no change to file structure
03AUG22 Add OBS_FILE as an option
12JUN22 Original