tic 
Pack ice that totally covers the entire sea surface with no open 
water is consolidated or compact (8/8); 7/8 coverage with 1/8 open 
water is very close, 6/8 to less than 7/8 coverage is close, 3/8 
to 6/8 is open, 1/8 to less than 3/8 is very open, less than 1/8 
is open water. The term ICE FREE is used if no sea ice is present 
(see for example Fig. 6 or 7). 
In connection with the ISP Commission VII Symposium in Banff, 
Alberta, Canada, in October 1974, the author again visited the 
US Fleet Weather Facility at Suitland. 
On my first visit there, in 1972, satellite-pictures from ESSA 9 
were used. They were taken at an altitude of about 1,450 km. In 
1974 a new satellite of the Mimbus series, "NIMBUS 5" (a NASA 
Meteorological R & D Satellite) had replaced ESSA 9. Nimbus 5 was 
the first weather satellite equipped with microwave radiometer, and 
therefore the first one which presented clear ice pictures day and 
night independent of covering clouds. Its orbit is near-polar and 
sun-synchronuous, at an altitude of about 1,200 km (APOGEE 1,252 km 
or 676 nautical miles, and PERIGEE 1,241 km or 670 n.m.); period 
107 min. 
The satellite has several sensors: a Temperature Humidity Infrared 
Radiometer (THIR); an Electrically Scanning Microwave Radiometer 
(ESMR), which provides Ice Edge information; an Infrared Temperature 
Profile Radiometer (ITPR); a Nimbus-E Microwave Spectrometer (NEMS); 
a Selective Chopper Radiometer (SCR), and a Surface Composition 
Mapping Radiometer (SCMR). 
The SCMR is a three-channel scanning radiometer (0.8 to 1.1 um, 
8.4 to 9.48 and 10.2 to 11.4 um). 
Nimbus 5 is mentioned in an Invited Paper for Commission I, XIIth 
International Congress in Ottawa, July-August 1972, by Frederick 
J. Doyle. U.S. Geological Survey, Washington, D.C., entitled 
IMAGING SENSORS FOR SPACE VEHICLES. 
The satellite in question has been used by the US Fleet Weather 
Facility ever since the 12 of December in 1972.