Several personal observations are offered on the NASA Propagation Program. The Science Review of the NASA Propagation Program held in September 1986 resulted in 14 principal recommendations. Current activities of the program reveal that the recommendations have in the main been successfully implemented and the program has evolved beyond conditions prevailing at the time of the review. A personal assessment of the current program is offered here

Rogers, David V.

English

NASA Technical Reports Server

N93-2648Z
OBSERVATIONS ON THE NASA PROPAGATION PROGRAM
David V. Rogers
Propagation Advisory Committee Representative
Communications Research Centre
Department of Communications, Ottawa, Canada
ABSTRACT--Several personal observations are offered on the NASA Propagation
Program.
1. INTRODUCTION
The Science Review of the NASA Propagation Program held in September 1986 resulted in
14 Principal Recommendations. Current activities of the program reveal that the recommendations
have in the main been successfully implemented and the program has evolved beyond conditions
prevailing at the time of the review. A personal assessment of the current program is offered here.
2. OBSERVATIONS
The activities reflected in presentations at NAPEX XVI and the associated ACTS
Miniworkshop reveal a vigorous and broadly-based program focused on problems of current
interest to the propagation and satellite-user communities. Participation by attendees from several
foreign countries and other U.S. national organizations show that cooperative efforts and active
monitoring of foreign propagation activities are being successfully pursued to the benefit of the
program. In the time since the Science Review of the NASA Propagation Program (Booker et al.,
1987), the recommendations of the Review Panel have generally been addressed successfully
within program constraints.
Not all recommendations were pursued to the same degree (nor deserved to be). The Panel
understood that it was NASA's duty to address the recommendations as appropriate within funding
and other constraints to promote program goals. Some recommendations became obsolete (e.g.,
the suggestion to investigate possible ACTS optical experiments became moot when the laser
communications package was deleted from the spacecraft). In some areas, the program has had
quite visible benefits, such as recent application of land mobile-satellite measurement results in
deliberations on radio spectrum allocations at WARC'92.
The level of attention in the case of Recommendation 7, which encouraged increased study
of intersystem interference caused by precipitation scatter and other mechanisms, might be
questioned. Though perhaps not so critical for the distributions of terminals characteristic of
present systems, interference theoretically is the ultimate limiting factor to deployment of
communication systems using the radio spectrum. The Panel concluded that NASA's previous
pioneering investigations of interference (in preparation for the 1979 WARC) should be reviewed
and updated.
In hindsight, this opinion was substantiated by the creation in 1990 of Task Group 3 of
CCIR Study Group 12, charged with a comprehensive review of procedures for calculating
coordination area in Appendix 28 of the Radio Regulations, and proposing modifications thereto.
TG 12-3 has recently concluded its work on Appendix 28, perhaps without benefit of sufficient
propagation information (a notable exception being results supplied for W. Europe from the COST
210 project). However, the motivation for the updating of Appendix 28 as well as the bases for
revisions appear to have been more political and commercial than technical, with substantial
182
https://ntrs.nasa.gov/search.jsp?R=19930017293 2020-03-17T05:39:30+00:00Z
reliance on practical systems experience over the past 20 years. The lack of broader-based
propagation data for interference applications does not seem to have had major negative
consequences, at least that are apparent at present.
3. CURRENT PROGRAM
Recently the propagation program has focused less on UHF/L-band frequencies used by
Land Mobile-Satellite Services, and more on propagation at Ka-band and higher frequencies, akin
to NASA's original propagation research interests. Redirection is of course impelled by the
impending launch of NASA's 30/20-GHz Advanced Communications Technology Satellite
(ACTS), and is consistent with current trends in satellite communication systems. NASA/JPL
preparations for propagation measurements with ACTS are well under way, preceded by
substantial and valuable equipment development and measurement phases with the Olympus
satellite.
The current program covers a broad array of studies: K-band propagation addressing
emerging requirements (low-margin systems, adaptive mitigation); satellite sound broadcasting at
L-band with plans for S-band measurements; areal rainfall features; EHF radiometric studies of
cloud attenuation; continuing development of handbooks, including the recent publication of
NASA Reference Publication 1274 for LMSS systems; and planning for investigations of K-band
mobile propagation (with ACTS) and LEO satellite systems. The participation at NAPEX XV and
the ACTS Miniworkshop confirms the recommended national and international cooperation.
I am impressed with the current activities of the Propagation Program. In consideration of
the small budget, I think the program achievements are in fact rather remarkable.
.
REFERENCE
H.G. Booker, G. Brussaard, K.S. McCormick, and D.V. Rogers, "Science Review of the
NASA Radio Propagation Program," Report STC-2127, Science & Technology
Corporation, Hampton, Virginia, February 1987.
183

ADVANCED COMMUNICATIONS
TECHNOLOGY SATELLITE
PROPAGATION STUDIES MINIWORKSHOP
Chairman:
Faramaz Davarian
Jet Propulsion Laboratory
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Observations on the NASA Propagation Program

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