-3- 
ERTS RBV 
ERTS MSS 
SL-S19QA 
SL-S190B 
Sensor 
Vidicon 
Scanner 
Frame camera 
Frame camera 
Record, format 
60x60 mm 
60x60 mm 
58x58 mm 
115x115 mm 
Record scale 
3,370,000 
3,370,000 
2,900,000 
945,000 
Ground resolution 
180 m 
300 m 
40 m 
10 m 
Coverage per frame 
185x185 km 
185x185 km 
174x174 km. 
108x108 km 
Based on these parameters the following orthophoto map products were 
predicted. 
ERTS-RBV 
ERTS MSS 
SL-190A 
SL-190B 
Map scale number 
1,000,000 
N 
250,000 
62,500 
Format 
6° x 4° 
0 
2° x 1° 
15’ x 15' 
Photos per sheet 
12-15 
N 
2-3 
1/2 
Map resolution 
6 ¿p/mm 
E 
7 ¿p/mm 
6 ¿p/mm 
Cartographic Products 
from ERTS 
The characteristics of the 
ERTS satellite 
are by now well known (2)* 
The vehicle flies in 
a circular 
orbit at 915 km 
altitute and 
97° indi- 
nation. It makes 14 
revolutions 
per day, and every 18 days 
the entire 
Earth (except for the polar areas.) passes beneath its Return Beam Vidicon 
(RBV) and Multi-Spectral Scanner (MSS) sensors. 
Tiie RBV is a 3-spectral-channel frame-format television system. Be 
fore launch it was anticipated that the RBV would have better ground reso 
lution and much better geometric fidelity than the MSS. It was contemplated 
that mapping would be done exclusively with the RBV. However a few days 
after launch the RBV was shut down because of electrical switching problems 
and has not been reactivated. 
The MSS has an oscillating mirror which reflects the scene through a 
Cassegrain telescope to a series of detectors. The image is recorded in 
4 spectral bands: green, red, and two near-infrared bands. The scanning 
aperture projected to the ground has a diameter of 79 m. This is equivalent 
to a photographic resolution of 220 to 320 m, depending on the scene con 
trast. The scanning motion covers a cross-track swath of 185 km, and 
spacecraft motion provides a continuous picture along track. 
The spacecraft also carries a tape recorder to store scenes acquired 
when out of range of the ground stations. The radio signals transmitted from 
the spacecraft are recorded on tape at the ground stations and sent to NASA 
Goddard Space Flight Center for processing. An Electron Beam Recorder (EBR) 
prints each spectral band as a separate black-and-white image on 70 mm roll 
film at an image scale of 1:3,370,000. The MSS images, though recorded 
continuously on the spacecraft, are printed as 185x185 km scenes by the EBR.