The following description of the AVCS systems is taken from the 

 "Nimbus 2 Users Guide."* 



The AVCS consists of three vidicon cameras and associated 

 electronics. The central camera is oriented downward along 

 the yaw axis (nominally the local vertical) while each of the 

 side cameras is mounted in the yaw-pitch plane at an angle 

 of 35 degrees to the central camera. Figure (15) shows the 

 Nimbus (2) television coverage, an area of approximately 1,900 

 by kOO nautical miles. Successive frames are taken at 9l-second 

 intervals providing about 20 percent overlap of earth coverage 

 at 600-nautical mile altitudes. Complete daylight orbital 

 coverage can be obtained with 32 consecutive picture triplets. 

 Successive orbits, displaced about 27 degrees westward in 

 longitude at the equator, provide adjacent pictorial data, 

 with increasing overlap from the Equator towards the poles. 



The AVCS pictures from the Nimbus satellites covered only a short 

 period of time — Nimbus 1, part of August and September l^Gk, and 

 Nimbus 2, late May through August I966. AVCS pictures from the ESSA 

 satellites, however, have been received on a nearly continuous basis 

 since the launching of ESSA 1 in February I966. As of December I968, 

 ESSA 3 has been turned off and 5 will be used on a standby basis; 

 ESSA 7 is transmitting clear television pictures on a daily basis. 



All of the AVCS pictures from both Nimbus and ESSA satellites are 

 archived. However, the transmissions received after 1 January I967 

 from ESSA 3 a^^e unique because all meso-scale arrays are stored in a 

 format suitable for computer manipulation. ESSA's National Environmental 

 Satellite Center (NESC) at Suitland, Maryland has formulated several 

 methods of working with the data, including global mosaics, brightness 

 composites, and gray toned enhancements. Examples of these are given 

 in Figures 16 and I7. 



^Although the Nimbus AVCS system described utilized the three camera system, 

 the ESSA satellite (TOS) achieves the same coverage with a single camera. 

 (Actually two cameras are aboard each ESSA satellite, but the data from 

 only one are used; the other acts as a backup camera). 



28 



