The nodal period was 108 minutes. Ascending nodes occur at 32 rainutes 

 before noon, local mean solar time. The orbit was very nearly sun-syn- 

 chronous; the drift rate of the orbital plane relative to the earth-sun 

 line was approximately half a degree per month. 



The Nimbus 2 spacecraft was essentially the same as Nimbus 1. The 

 major differences between the two spacecraft were the addition of the 

 MRIR to the sensory ring and the provision for immediate broadcast of 

 nighttime HRIR data that could be received by modified APT ground station 

 equipment. 



55 



