This page is designed as a dynamic
repository of relevant information to aid users of ASCAT enhanced
resolution image products. Additional information is available here
as a pdf document.
Enhanced resolution images made from ASCAT data are created
from SZF files using the multi-variate the Scatterometer Image
Reconstruction (SIR) algorithm with filtering (SIRF). Like
previous fan-beam scatterometers, ASCAT collects measurements
at multiple incidence angles and up to 6 azimuth angles.
The effective image resolution
varies depending on region and sampling conditions but is estimated
to be 12-15 km in most areas. The SIRF algorithm makes A
images at 4.45 km pixel spacing.
Multiple passes of the spacecraft are combined to
produce a higher spatial resolution (at a cost of reduced temporal
ASCAT data was obtained the PO.DAAC. No recalibration has been applied.
Due to its polar orbit, the local-time-of-day of the ASCAT
observations varies with latitude and direction of the orbit. At mid-
to low-latitudes, most areas are imaged at two different local
times-of-day -- one for the ascending (north-bound) pass and one for
the descending (south-bound) pass. Thus, by separating the data into
ascending and descending passes, images corresponding to two different
local times-of-day are created. In the polar regions, particular
locations are observed at multiple local times-of-day and so a
different method is required. Local time-of-day is considered in more
detail in MERS research report.