SECTION 5. REQUIREMENTS 



The Ocean Color Science Working Group (OCSWG) spent a considerable amount 

 of time attempting to specify the limitations and compromises of a MAREX 

 satellite monitoring system. From this background, a set of minimum space- 

 craft and ground system requirements were identified in order to accomp- 

 lish the major scientific opportunities from space-borne ocean color data. 

 To propose a system which would satisfy all possible users, research and 

 operational, is beyond the scope of this report and also is unrealistic to 

 expect. As a result, only the experiments (Table 4-2) discussed earlier in 

 the report are being considered in framing requirements. Thus, this pro- 

 vides the focus for the requirements allowing significant scientific 

 progress in limited well-defined programs, while still offerinq sufficient 

 flexibility to satisfy a reasonable proportion of the needs of other 

 scientific and operational areas. This report will provide the basis for 

 further development in color sensing science in other fields in the future 

 as well as execute an exciting nearer term shelf carbon/nitrogen flux 

 experiment. The minimum requirements for an ocean color system which could 

 receive the support of a significant portion of the oceanographic commu- 

 nity are discussed in this section. While there are a number of possible 

 system scenarios, it is recommended that NASA proceed with a formal study 

 of a system to meet minimum data requirements. 



5.1 SPACECRAFT 



At the present time, the only polar orbiting spacecraft operated by the 

 United States civilian space program that can support the CZCS mission is 

 one of the advanced TIROS-N (ATN) series (Table 5-1). Two NOAA satellites, 

 NOAA-6 and NOAA-7, are in near polar sun synchronous orbits crossinq the 

 equator at 7:30 a.m. and 7:30 p.m. for NOAA-6, and 2:30 p.m. and 2:30 a.m. 

 for NOAA-7. In order for the CZCS to be most effective, the desired 

 crossing time at the equator is near noon, so that the sun is either ahead 

 or behind the spacecraft to minimize the effect of sun reflection (glint) 

 directly into the sensor during the +40 degree side scan. The OCSWG 

 addressed the question of whether the spacecraft could orbit with a 1:30 

 p.m. and 1:30 a.m. equatorial crossing time with an ascending node orbit 



5-1 



