willner@cfa250.harvard.edu (Steve Willner P-316 x57123) (03/30/89)
From article <386@illusion.UUCP>, by marcus@illusion.UUCP (Marcus Hall): > ... the ground stations would > need upgrading to get the communication capacity of the TDRSS, and even then > it would not provide the constant coverage required for efficient use of > the HST, etc. In current planning, HST and other scientific missions will not have continuous access to TDRSS. The short access periods allowed will have to be scheduled far in advance and even then may be preempted by "higher priority needs". Being forced to use TDRSS is actually a severe constraint on the operation of scientific missions. The benefit of TDRSS, of course, is that it gives nearly continuous communications with missions of sufficient priority. (Read "Shuttle missions"). While this is all very well and may justify the cost of TDRSS, the policy of forcing other missions to use TDRSS is essentially a political decision similar to the one a few years ago to force all payloads to use the Shuttle. ("We've spent all that money on it, so you have to use it!") Now that expendables are allowed again, some mission planners are looking at using high orbits at least in part in order to bypass TDRSS. -- Steve Willner Phone 617-495-7123 Bitnet: willner@cfa 60 Garden St. FTS: 830-7123 UUCP: willner@cfa Cambridge, MA 02138 USA Internet: willner@cfa.harvard.edu
dietz@cs.rochester.edu (Paul Dietz) (03/31/89)
The main reason for TDRSS is to be able to communicate with spy satellites. Imagine radar satellites like Lacrosse have insatiable appetite for bandwidth, and they need this bandwidth while over areas where there are no cooperative ground stations (i.e., the USSR). See the latest issue of Science for an article on the subject. HST users cannot know when TDRSS will be preempted, making scheduling a challenge. Paul F. Dietz dietz@cs.rochester.edu