The ATSR Project

In order to help visualise the ground coverage of the ATSR-2 swath the following plots have been prepared.
There are two sets of plots viz High Rate Coverage and IDHT Descoping Regions.

High Rate Coverage - The instrument data handling system operates in several modes as described in the ATSR Handbook, basically due to data bandwidth limitations on the low bitrate (LBR) payload experiments and data rates change throughout the orbit based on a series of constraints. Without going into detail which are embedded in the ERS Mission Planning rules, ATSR-2 highrate data, where data from all 7 detectors are downlinked at full resolution occurs on the day-side of the orbit and only over land. At all other times the instrument data handler operates in low-rate flexible format where there are varying degrees of data compression and or limitation.

IDHT Descoping Regions - The IDHT is the ERS Instrument Data Handling and Transmission system, the crucial component of which is the onboard tape recorder. Due to constraints of the the four ground stations coverage for downlinking the recorded data, it is not possible to record and subsequently transmit a complete data set. The ERS mission planning system attempts to optimise the global coverage of the LBR instruments but cannot achieve 100%. The plots shown here give an indication again in the form of a normal ATSR swath pattern missing data that is never collected because of the mission planning descoping.

All the plots each cover 501 orbits of ERS-2 by Cycle Numbers as defined in the ERS Mission Scenario, the actual orbit number range and dates are given on each plot. The plots trace a swath which equates to the nominal 512Km wide scene on the earth surface when the instrument data collection mode was in High Rate or Descoped.

What can be visualised is the systematic build up in each ERS-2 Cycle of the global coverage by the instrument. There are within the ERS mission planning system regionalised priorities given to the areas of descoping.

Potential users of ATSR data, particulary of the visible channels, may find the High Rate plots useful for selecting regions of interest for studies,for example it would not be very productive to request day-time or descending data over the Indian sub continent.

Swath Data

Page last modified : Tuesday, 04-Dec-07