Annu. Rev. Astron. Astrophys. 1991. 29: 89-127 Copyright © 1991 by Annual Reviews. All rights reserved

5.4 Apollo-Soyuz

What are the data from Apollo-Soyuz that are in dispute? They are presented in Figure 15, for the northern galactic hemisphere. Detections at a level of ~ 300 units are shown in that diagram over large regions at moderate and high Galactic latitudes, and cosmic backgrounds of thousands of units are also seen at all Galactic latitudes, including the highest.

Figure 15. Henry (32) translated the Apollo-Soyuz count rates of Paresce et al (91) into units and presented this and a corresponding figure for the souther galactic hemisphere. It is argued in the text that the lower bounds of ~ 300 or 400 units are of great significance in the study of diffuse ultraviolet background radiation, but that the high levels are spurious.

These results contradict the many results discussed in the previous sections. From that discussion one can doubt any detections in Figure 15. Nevertheless, Paresce et al (92) attempted to extract from among the 3200 total Apollo-Soyuz observations, some positive detections that might contain astrophysical information. They located 128 measurements that provided four correlations of intensity with hydrogen column density. A critical discussion of the Apollo-Soyuz data as analysed by Paresce et al (92) is given elsewhere (32).

We are left with upper limits from Apollo-Soyuz. But nevertheless these upper limits are of great importance in trying to understand the origin of the diffuse ultraviolet background, now to be discussed.