APPENDIX D 

 ERTS-A EVALUATED 



by LTJG S. R. OSMER, USCG 



In October 1972, Commander, International Ice All bands were in the visible spectrum for day- 

 Patrol began receiving ERTS-A imagery cover- light operation. Bands 6 and 7 were near-infra- 

 ing the Grand Banks north to 60°N. This is the. red bands. Photographic products were received 

 conclusion reached from two years of viewing in two sizes — 70mm and 9.5 inch positive trans- 

 this satellite imagery. parencies. The respective scales were 1 :3,369,000 



ERTS-A (Earth Resources Technology Satel- and 1:1,000,000. 



lite) was launched on 23 July 1972. The life The MSS gathered data by imaging the sur- 



expectancy was one year. Imagery was still face of the earth in several spectral bands simul- 



being beamed to earth when ERTS-B was taneously through the same optical system. It 



launched on 19 January 1975. scaned crosstrack swaths of 185 kilometers (100- 



The ERTS mission was to gather high resolu- nm ) sa . uare width - 



tion multispectral data of the earth's surface The MSS precision output product had a re- 



on a global basis. The sensor payload contained sidual error for positional mapping accuracy of 



two systems to accomplish this mission — a four 242 meters. 



channel Multispectral Scanner System (MSS) The July 1972 issue of Aviation Week and 



and a three camera Return Beam Vidicon (RBV) Space Technology stated the operating resolution 



system, of the MSS was expected to be about 225 feet. 



The following descriptions are from the ERTS The September 1973 issue of Environmental Data 



Data Users Handbook. ERTS-A operated in a Service stated ERTS was capable of resolution 



circular sun synchronous, near-polar orbit at an approaching 100 meters (about 330 feet), 



altitude of 494 nautical miles. It circled the Thomas Ragland, Assistant Project Manager 



earth every 103 minutes, completing 14 orbits per ERTS/NIMBUS, NASA/GSFC, in correspond- 



day and viewed the entire earth every 18 days. ence with International Ice Patrol Headquarters 



The orbit was selected and kept trimmed so that in Jul y 1972 > stated that MSS Bands 5 and 6 



the satellite ground trace repeated its earth cov- were best for sighting icebergs. Under cloud free 



erage at the same local time every 18 day period conditions because of the good contrast between 



•xi • ™ A - i -n the ice and water in these bands, icebergs with 



within 20 nautical miles. , , , , n ' , ., 



exposed areas down to about 0.02 square kilo- 



The RBV operated in the range of 0.48 to 0.83 meter (aQ1 gquare mileg) QmM expect to be ^ 



micrometers visible wavelengths. Each camera „ ,-. n „^\ , t ,, , ■ * n 



, , Barnes (19*3) stated that ice features as small 



sensed a diferent spectral band. However, due ag gmaU floeg (2Q to mm) acrogs ^^ be de _ 



to its large power demand, this system was rarely tected He algo gtated that the MSS ^ and 



usec '- MSS-5 bands appeared to be best for mapping 

 The MSS imagery was viewed by the Ice ice boundaries, whereas the MSS-7 band pro- 

 Patrol. The four bands of the MSS were: vided greater detail in the ice features. After a 



t, , . _ „ . _ limited examination of color products, he felt 



Band 4 0.O-0.6 micrometers ,, .„ -, f ■ J ± 



there was no significant advantage in the use ot 



Band 5 0.6-0.7 micrometers color datft {m ice mapping . The size of features 



Band 6 0.7-0.8 micrometers somewhat smaller than 100m across could be 



Band 7 0.8-1.1 micrometers measured from enlarged ERTS prints. Most im- 



27 



