Polar Waveform Data Reference Set from Seasat Altimeter Sensor Data Record

The PDRS (Polar Data Reference Set) is a subset of the Seasat Altimeter sensor
data record (SDR) archive maintained at the ADF (Algorithm Development
Facility), part of the EODC (Earth Observation Data Centre). The aim was to
provide a manageable set of polar waveforms for R&D analysis. The PDRS covers
a 17-day repeat period from 24th July 1978 to 11th August 1978.

Seasat was launched on 28th June 1978 carrying a five-sensor payload. The
objective of the Altimeter (ALT) was to determine ocean topography with a
height measurement precision of 10 cm. The ALT carrier frequency was 13.5 GHz
and operated in chirp pulse mode with a 3.2 micro-second uncompressed pulse
width and 3.125 ns compressed pulse width. The pulse limited footprint
diameter was 1.2 km for calm seas; beam-limited footprint diameter was 22.2
km.

The PDRS is sub-divided into four data types: i) Antarctic ice sheet data,
ii) Antarctic sea ice data, iii) Greenland ice sheet data, and iv) Arctic sea
ice data.

The source of the PDRS data set was 36 tapes comprising the SDR waveform data
for a 17-day repeat period. The data points of interest fall in two distinct
geographic regions: south of -50 and north of 59 latitudes. In the southern
region, all data with the TOIL flag set to land were extracted as Antarctic
ice sheet data. In the northern region, all data with the TOIL flag set to
land within Greenland (longitudes -58 W and -20 W) were extracted as Greenland
ice sheet data

The remaining sets of sea ice data were extracted using an algorithm based on
the peakiness of the waveform which was developed by the Remote Sensing Group
at Mullard Space Science Laboratories, UK.

The tapes are written in 9-track, 6250-bpi format. The block format is that
described in the Seast Telemetry dictionary, containing 23 waveforms packed
into 2988 2-byte words. Each tape is divided into logical files separated by
a file mark, one per source tape.

Full tape copies will be made of this data set on request. Tape handling
costs will be charged.