Landsat coverage statistics

[Serge Andrefouet]

Dear colleagues,

Last week(12-14th October), the first Landsat Science Team Meeting after
the launch of Landsat 7 took place in Goddard Space Flight Center (GSFC) in
Maryland. Terry Arvidson (GSFC), John Gasch (GSFC) and Samuel Goward (L7
Science Team chairman) presented the last statistics in terms of coral reef
coverage, among other "niches" (volcanoes, rainforest, agricultural areas,
oceanic islands, calibration sites, sea ice and glacier). 
Here, I quote their report, that will be published in the proceedings of
the 14th Pecora Memorial Remote Sensing Conference (6-10 dec. 1999 - Denver
Colorado):

"There are a total of 8742 reefs covered by 968 scenes in the land database
and therefore in the LTAP. 19 scenes (21 reefs) are isolated scenes that
have a heavy overhead associated with their acquisition because of
isolation. After a year of operation, the addition of these scenes to the
database will be reconsidered.
The scenes with reefs were further reviewed: high priority was assigned to
111 scenes containing a total of 604 reefs that ate currently at risk,
currently under study, or planned for study in the near future. 
Acquisition frequencies: As requested, potential research sites are slated
for acquisition twice each year, at the peak of bleaching in the late local
summer and six months later, and existing research sites are acquired on a
quaterly basis. In reality, many scenes containing reefs are acquired much
more frequently because they are driven by the land content of the scene,
not the reef content: 70% of the 8748 reefs have acquisition rates twice a
year or better, 65% have acquisition rate of 4 times a year or better, and
33% have rates indicating they are to be acquired every opportunity. Of the
604 high priority reefs, 0.8% have acquisition rates of twice yearly, 6
months apart; 45.5% have acquisition rates of quaterly and 53.7 % have
rates of acquisition greater than 12 times a year.
Acquisition results to date: Since the start of routine operations on July
15, we have acquired 1054 images covering 82% of all the requested reefs.
Acquisition rates for scenes containing reefs ranged from one to six times. "

This report shows that the rate of acquisition will be much higher than
requested for most of the reefs worldwide. Some areas covered during the
first months of operation still suffer from cloud coverage but the
situation will likely  improve in a near future, after that seasonal
patterns in cloud coverage change.

Hope it informs,

Serge





Serge Andrefouet
Department of Marine Science
Remote Sensing/ Biological Oceanography
University of South Florida              
140, 7th Av. South                       
St Petersburg 
FL 33701

phone: (727) 553-1186
fax:   (727) 553-1103
E-mail: serge at carbon.marine.usf.edu