A group of propagation researchers have joined to prepare for a major campaign of propagation experiments for fixed satellite services using the Olympus satellite. For several years, the receiving hardware and data processing procedures have been planned, now, with the launch of the Olympus satellite imminent, experimenters are eager to start the real work. A short review is given of the accomplishments made since the last NAPEX meeting

Arbesser-Rastburg, Bertram

Turney, Owen

English

NASA Technical Reports Server

N90-17961
RECENT ACHIEVEMENTS OF OPEX
Bertram Arbesser-Rastburg and Owen Turney
European Space Research and Technology Centre
Noordwijk, The Netherlands
Abstract: A group of propagation researchers have joined to
prepare for a major campaign of propagation experiments for fixed
satellite services using the Olympus satellite. For several years
the receiving hardware and data processing procedures have been
planned, now, with the launch of the Olympus satellite imminen t
experimenters are eager to start the "real work". The aim of this
paper is to give a short review of the accomplishments made since
the last NAPEX meeting.
i. Introduction
The launch of the European Space Agency's (ESA) OLYMPUS
experimental satellite is scheduled for mid 1989. This marks the
entry into a new phase for the OLYMPUS Propagation EXperiment
(OPEX) group. Some of the experimenters are already fully prepared
to start the measurements; the coding of the data processing
software is underway and the communication links for distributing
vital information are being set up.
2. The OPEX Group
OPEX was set up under ESA auspices in 1980 with the objective
of standardizing the essential procedures in equipment calibration
and data handling necessary to achieve results that are directly
comparable. Much experience was drawn from the COST (CoOperation
Scientifique et Technique) activities (actions 25 and 205) that had
led to the first Europe-wide collection of Ku-band satellite
propagation statistics (Fedi, 1985). Further details on the
development of OPEX can be found in the referenced literature
(Brussaard, 1988).
Today the OPEX community includes approximately 70
organisations. Of these, about 30 are preparing to make
measurements. They are equally divided amongst:
- Universities
- PTTs or Telecommunication entities
- Private or governmental research institutions
Three of the participants are from outside Europe, namely:
- CRC in Ottawa, Canada
- Virginia Tech in Blacksburg, VA
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https://ntrs.nasa.gov/search.jsp?R=19900008645 2020-03-20T00:06:59+00:00Z
- North Carolina State University in Rayleigh, NC.
The chairman of the OPEX group is Professor Gert Brussaard from
the Technical University of Eindhoven in the Netherlands.
3. ESA's role in OPEX
ESA has the overall responsibility of the satellite mission
and also has taken on responsibility for three principal aspects
of the OPEX collaboration:
- to act as a focal point
- to study new hardware designs for receivers and radiometers
- to have the common data processing software developed
The Propagation Section at ESTEC is in charge of these
activities and some more details with particular respect to recent
achievements are given below.
3.1 Coordination
ESA is providing an administrative and organisational infra-
structure which gives the OPEX group a focal point for information
and coordination. Up to now this function mainly concentrated on
keeping an electronic mailing list, organizing the OPEX meetings
and producing proceedings of the meetings.
More recently a database with information on the different
propagation experiments has been established which allows the scope
for co-operation between experimenters to be quickly assessed,
either in getting their hardware operational or in exchanging data.
In the future (once the satellite is in orbit) also the regular
dissemination of orbital element data and manoeuvre information
will be provided. Communication will be via telex, e-mail and fax.
One of the difficult points in coordinating this collaborative
activity is the fact that there is some diversity in the size and
scope of individual experiments and in the finances available.
This also means that not all the groups arrive at the same level
of readiness simultaneously. However, the general enthusiasm of
the experimenters and the openness of the discussions make it easy
to deal with these discrepancies.
With the number of active experimenters close to 30 it was
also found useful to set up smaller working groups of specialists
to examine in detail particular questions and to apply their
expertise to important decisions. Such a "small user group" was
established to monitor the development of software.
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3.2 Hardware studies
The Agency has contracted out theoretical and development
studies relating to experimental hardware. Specifically the areas
of Beacon Receivers and Radiometers were investigated. To this end
two studies were completed recently:
- The digital beacon receiver which had been developed by Signal
Processors Ltd (Cambridge, U.K.) was delivered to ESTEC as a
functional prototype for one receive channel. Instead of a PLL
a digital Fourier transform processor is used for carrier
frequency tracking. This allows tracking of the signal down to
a C/No level of about 15 dB below the point where a PLL
receiver (50 Hz loop-BW) "drops out".
- The study of a 20/30 GHz radiometer to measure the liquid
water and the water vapor content of the atmosphere has
resulted in a design recommendation that combines high
accuracy, simple maintenance and low price. The study was
carried out by FARRANTechnology (Ballincollig, Ireland)
Apart from these studies directly relevant to OPEX, ESA is
also planning for future propagation experiments.
The 44.6/89.2/133.7 GHz beacon payload for the next generation ESA
communication satellite (SAT-2) has been studied by Contraves
Italiana (Rome, Italy). The study showed that such a payload can
be realized with a total weight of less than 15 kg (with redundancy
on all active components) and a power consumption of less than 50
Watts.
3.3 Data Processing Software Development
The OPEX group considered in detail standard procedures for
both earth station dependent data processing and station
independent data analysis. The aim being to ensure that the
formation of event data and its subsequent comparison and exchange
could be carried out without worries regarding varying data
treatment procedures.
ESA placed a contract with Siemens Austria and CSR Ltd (U.K.)
for the study of standardized procedures and software for the
processing of propagation data. This study resulted in a clear
definition of the software requirements and the architectural
design and was completed in January 1989.
Now the contract for the development of the software is
underway and will be completed by May 1990. The work is being
carried out by Siemens Austria (Vienna) with support from IAS
(Graz, Austria). The software design and development must take
into account the different computer systems used by the
experimenters. To ensure portability UNIX and VMS have been chosen
as operating systems and a limited number of computer systems are
going to be supported. The chosen targets are 80386 based PCs with
165
AT bus, VaxStations and HP9000 workstations. The adoption of
"standard" software tools and packages was also found to be a
necessity. The WIMP (Windows, Icons, Mouse, Pointing) based
interface "X-Windows" and the graphics package "GKS" (Graphical
Kernel System) were selected for the human-computer-interface and
for graphics respectively. The programming language chosen is "C"
and the C-ISAM library is used for data and file handling tasks.
The design was user driven at all stages. This involved
frequent liaison and demonstrations with the so called Small User
Group, representing the wider body of OPEX. On completion of the
software development full documentation including a Software User
Manual will be issued to users.
4. OPEX Meetings
Two OPEX meetings have been held since last summer. The first
one, OPEX ii was held in June 1988 in Copenhagen, being hosted by
the Danish PTT. There were more than 50 participants representing
nearly all experimenters and some of the companies involved in the
design of experimental hardware and software.
OPEX 12 took place in Vienna in April 1989 with the
support of Siemens Austria and T.U. Graz. Again, close to 60
people turned up. The status of the satellite and payload as well
as the ground segment and standardized software were discussed in
detail. Numerous presentations were also given on both, status of
preparations as well as useful observations relevant to making
propagation measurements. All papers and reports were jointly
published in conference proceedings. For the OPEX group the
OLYMPUS Utilisation Conference which also took place in Vienna
immediately after the OPEX meeting provided an ideal opportunity
to find out about the four other OLYMPUS payloads and their uses.
A redraft of the OLYMPUS Propagation Package User Guide was also
issued, containing important results of tests on the payload
transmit system.
5. Plans
After the Olympus satellite has reached its final orbital
position at 19 deg West (approximately 22 days after launch), a
phase of careful in-orbit testing will commence. This will take
over two months. The beacon payload will be tested for e.i.r.p.
(co- and cross-polar), polarisation orientation, power- and
frequency stability and phase noise. The tests will be carried
out in Redu (Belgium) using specially built measurement stations.
After completion of the IOT the propagation measurements can start.
The software development will arrive at a down-scaled
prototype of the pre-processing package in November of this year
and the final acceptance test (for the 80386-software) is scheduled
166
for April 1990. It is planned to have a small training workshop
for the users at this time.
6. Conclusion
It has been a busy and productive year for OPEX. The preparation
of facilities to receive the OLYMPUSpropagation beacons made a big
step forward in most places. Some old ground stations have been
refurbished, many have been constructed "from scratch" and are
ready to start measurements as soon as they can pick up a signal
from 19 degrees West. We are all confident that the careful
planning, attention to detail and co-operation on a wide scale will
ensure the success of this campaign.
References
Brussaard, G. "The Olympus Propagation Experiment OPEX: A Unique
Example of European Cooperation", ESA Bulletin, No 54, pp. 34-
38, May 1988
Brussaard, G. "OPEX- Olympus Propagation Experiment", Proceedings
NAPEX XII, Syracuse, N89-II090, pp. 140-145, Aug 1988
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NAPEX XIII
San Jose
30 June 1989
XEP
Section
TIME CHART OLYMPUS DATA PROCESSIN_
|
I YEAR
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I ADD
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I DDD, CODE
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I LAUNCH
I START MEAS.
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1988 I
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URD...USER REOUIREMENT DOCUMENT
SRD...SOFTWARE REQUIREMENT DOCUMENT
ADD...ARCHITECTURAL DESIGN DOCUMENT
DDD...DETAILED DESIGN DOCUMENT
168


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