JET PROPULSION LABORATORY                 INTEROFFICE MEMORANDUM

                                          TBK 94-007

                                          February 6, 1994


TO:         N. R. HAYNES

FROM:       T. B. H. KUIPER

SUBJECT:    ON THE ROLE OF RADIO ASTRONOMY IN THE DSN



                                  Summary

     Radio astronomy has enhanced the DSN's mission by helping to
develop many of the critical technologies that are in use in the
Network today. Often, radio astronomy observations are among the
most demanding on Network systems and hence tend to challenge DSN
R&D, engineering, and operations - resulting in a better and more
reliable DSN for our planetary mission customers.

     This memo describes some of the contributions which radio
astronomers make toward enhancing the operational efficiency of
the DSN.

     *	  Certain astronomical techniques enhance DSN operations
          by providing an additional set of methods and equipment
          that have proved invaluable for both routine and
          unusual operations.
     *	  Radio astronomers, by their use of non-standard DSN
          systems, ensure that these systems are actually working
          when they are needed for non-nominal mission events.
     *	  Astronomical observations, by their very nature,
          provide technical challenges for DSN engineers and
          operators.
     *	  Radio astronomers often provide field testing of
          advanced equipment under operational conditions, thus
          accelerating the transfer of new technology into the
          DSN.
     *	  The radio astronomy mission provides a rationale for
          extending the capabilities of the DSN in ways that
          often lead to improved support of flight projects in
          the future.
     *	  Joint activities with non-DSN radio observatories
          create and maintain relationships that can lead to
          better support of flight projects through interagency
          tracking or arraying.
     *	  Radio astronomy provides a set of people skilled in key
          technologies that are important to the DSN's main
          missions.

     The result of these contributions has been, and will
continue to be, a better and more cost effective DSN.




                               Introduction

     The DSN and radio astronomy have developed a productive
symbiotic relationship over the past thirty years. Radio
astronomy has helped to develop many of the critical technologies
that are in use in the Network today. Radio astronomy operations
are among the most demanding on Network systems and hence 
challenge the DSN to achieve its best performance.

     The DSN is widely recognized as a key contributor to radio
astronomical research. The document The Deep Space Network - An
Instrument for Radio Astronomy Research recounts the history of
the DSN at the forefront of radio astronomy.  Astronomers
continue to use the unique capabilities of the DSN to work at the
cutting edge of research on galactic nuclei, black holes,
supernovae, evolution of interstellar clouds, interstellar
chemistry, star formation, stellar emission mechanisms, stellar
envelopes, astrometry and geodesy.  This research has provided
the DSN with an invigorating stimulus for innovation and renewal.

     It is not surprising that the relationship between radio
astronomy and the DSN has been so productive. Gathering telemetry
from weak transmitters at the edge of the Solar System has much
more in common with radio astronomy that with near-Earth
communications. Thus, the 26-m and 70-m subnets trace their
heritage directly to astronomical telescopes, and if there is
ever a new generation of large DSN antennas, they will inherit
the experience obtained from the Bonn and Green Bank 100-m
telescopes.  Both the DSN and radio astronomy share ultra-low
noise receiver technology for the same reason.

     Below, some of the contributions to DSN technology and
operations which resulted from the activities of radio
astronomers using the DSN are listed along with the names of the
scientists first involved with those activities and the
approximate date.
- digital spectrometers (Goldstein 1963)
- VLBI (Moffett, Ekers 1967)
- antenna calibration with natural radio sources (Klein 1972)
- connected interferometry (Gulkis, Jauncey 1979)
- antenna pointing models (Peters, Rius 1982)
- K-band masers (Gulkis, Jauncey, Kuiper 1982)
- Internet service to Complexes (Kuiper 1993)
The radio astronomical contributions consisted of a mix of
technological, methodological, and operational innovations.

     The technique of VLBI, which began in the DSN with the
observations of Moffett and Ekers, proved to be particularly
important.  The continuing involvement of JPL astronomers has led
to the exploitation of VLBI for determination station location
and synchronization of Complex frequency standard clocks, of
differential VLBI for spacecraft navigation and the supporting
astronomical source catalogs, to advanced correlators and
recorders.  The recorder technology in turn spun off the
technology for data arraying.


Astronomy equipment enhances DSN capability

     Activities of astronomers result in DSN having extra
capabilities beyond those currently needed for deep space
communications.  The K-band masers installed on the 70-m antennas
give NASA and JPL the opportunity to participate visibly in the
upcoming international Space VLBI missions, in addition to
providing telecommunications service.

     We are currently extending the frequency coverage of DSS-13
to 50 GHz.  We are also working to extend the frequency coverage
of that station's 32/34 GHz system.

     The high spectral resolution wideband spectrometers in the 
Canberra and Goldstone Complexes are available for emergency
spacecraft acquisition, when signals due unlocked spacecraft
transmitters are too weak or have drifted too far to detect by
the usual methods. The most recent examples of this were the
searches requested by the Mars Observer project for the
spacecraft and then the Mars Balloon Relay with the HRMS
spectrometer. 


Radio astronomy provides technical challenges for DSN engineers

     Routine DSN operations are boring.  Successful operations
are supposed to be. If things are happening which make Complex
engineers' adrenalin flow, spacecraft data acquisition is in
jeopardy.  Yet, Complex Directors want to be able to retain high
quality personnel, the kind of personnel who will look for
challenging positions.  Both Mike Dinn (Canberra) and Jose Urech
(Madrid) have told me that they encourage radio astronomy because
it provides technical challenges for their professional staff.


Radio astronomy ensures DSN functionality

     The DSN has been designed with a tremendous range of
capabilities.  Many of these capabilities are seldom exercised. 
For example, the subreflector is almost never rotated for normal
operations.  Radio astronomy, however, uses many of these
capabilities.  In addition, astronomers are always looking for
the ultimate performance, so that DSN capabilities receive close
scrutiny.  This often uncovers unsuspected problems.

     In the late 60s, when Sam Gulkis began polarization
measurements of Jupiter's magnetosphere to determine the rotation
period of the planet's core, he discovered that the DSS-14
polarization was 45ø out of spec.

     Throughout the 1970s, Mike Klein and Charles Stelzried
reported early warning signs of maser cryogenic problems. Their
sensitive radio astronomy observations showed increased noise
instability about two weeks before the LNA performance degraded
enough to affect spacecraft tracking requirements.

      Antenna measurements at high frequencies above the Ruze
limit are very sensitive indicators of antenna performance, as
Bob Stevens often pointed out. In 1974, Art Niell and I reported
that the upgrade of DSS-14 in February and March of 1973 had
resulted in a decrease of aperture efficiency of 0.5 dB at 8.4
GHz and 1.6 dB at 15 GHz. Last year, various observations
conducted by V. Altunin, T. Velusamy, and others have shown that
since the Landers earthquake DSS-14 has about 70% of the
efficiency at 22 GHz compared to the other 70-m antennas.

     K-band operations continually turn up changes in the antenna
pointing characteristics. Indeed, it was this variability which
drove astronomers using the DSN 70-m at 15 GHz and above to
develop pointing models for these antennas long before the DSN
recognized a need for such models.

     This summer, when the DSN upgraded the VLBI recorders to
high density heads, VLBI observations led to the detection of a
cabling error, which was compensated in software.

     By operating and calibrating the antennas at the limits of
their performance, radio astronomy helps to ensure the
functionality of their capabilities and ensures that these are
available when needed.  It will be especially important in next
years leading up to Space VLBI mission operations to use radio
astronomy activities to hone the DSN's technical and operational
performance at K-band.


Radio astronomy field-tests advanced systems

     TDA supports the development of new receivers and other
equipment which may one day be used to enhance the capabilities
of the DSN. Radio astronomy often uses such developmental
equipment as soon as it is installed.  The first receiver I ever
used was the 15 GHz maser installed at DSS-14, a combination
which at the time was far and away the most sensitive in the
world.  We used it for many years and so provided a long
performance history for it.

     The radio spectroscopy research project at JPL into the
fragmented structure of star forming molecular cloud cores would
be extremely enthusiastic about using Ka-band receivers on the
70-m antennas.  Likewise, there would be keen interest for using
arrayed feeds to improve high frequency performance and/or to
achieve multiple beams.

     We are working with TDA Engineering towards achieving the
policies and security tools which will permit full Internet
connectivity for the DSN.  The ultimate goal is to enable remote
and automated radio astronomy operations, first at DSS-13 and
eventually on the 70-m subnet. This capability would also be a
highly valuable tool for solving mission support problems quickly
when they arise.



Joint radio astronomy activities with radio observatories builds
good relations

     When the DSN is used in joint astronomy activities, such as
VLBI observations, or when the DSN is used to complement
capabilities of radio observatories, contacts are developed and
maintained which benefit the DSN and the missions it supports. 
The support provided by the VLA and Parkes to Voyager encounters,
and the joint HEMT LNA development in preparation for that, are
the most notable recent examples of this.

     Less well known is the fact that two of the three 18-26 GHz
masers in the DSN are on loan from NRAO.  The technology was
first developed at JPL and then transferred to NRAO and other
observatories.  These receivers have been used in the DSN to
refine antenna pointing and gain calibration models, and they
will enable the DSN to participate in the upcoming Space VLBI
missions by contributing essential co-observations.


Astronomical techniques enhance DSN operations

     Having people who do astronomy with DSN facilities provides
a pathway whereby astronomical techniques are adapted for DSN
operations.  The development of gain and pointing models using
radio sources are examples of this.  The techniques developed by
Mike Klein to make high precision measurements of the fluxes of
the outer planets are still used today to calibrate the gain of
the antennas.  When it was realized well into the Voyager mission
that the 70-m antennas did not have good enough blind pointing
capability to acquire the spacecraft at the instant of emergence
from behind the planet, the pointing models and associated tools
developed by Bill Peters in Australia and Antonio Rius in Madrid
were quickly incorporated into DSN tracking operations through
the work of Bob Riggs, a TDA 440 engineer.

     Other examples of radio astronomy techniques adapted to DSN
operations are the use of VLBI to synchronize the station time
references, to determine precise station location, and to
determine spacecraft positions precisely.  When the DSN wanted to
explore the effectiveness of holography methods for measuring
antenna deformation, another technique pioneered by radio
astronomers, the Tidbinbilla Interferometer was used to make this
assessment.


Radio astronomy provides a rationale for extending DSN
capabilities

     Radio astronomers would often like capabilities which the
DSN does not currently have.  One example is the ability to put
operations (Complex operations and radio astronomy data
acquisition) under control of a non-DSN computer, directed in
real time for non-standard activities such as radio astronomy
research or engineering tests.  Two separate approaches developed
in Australia and Madrid were adopted locally to automate the
gathering pointing and gain data. 

     This case has an interesting lesson on how the 'system'
creates obstacles, and how they can be worked around.  When Bob
Riggs first started to worry about gathering antenna pointing and
gain data, we investigated the possibility of putting a computer
we could program on the Complex LAN and found it bureaucratically
intractable.  That is, neither of us could afford the cost of
negotiating and documentating interface agreements.  The cost of
actually making the software mods was minor by comparison.

     A general solution was eventually found.  Madrid has locally
developed a PC-based version of the Link Monitor Console (from
which operators control antennas) for training and testing. 
Madrid agreed to assemble, with TDA management agreement, a
second such system that has a serial port over which a radio
astronomy (or other activity) computer can send antenna commands
to be processed in the usual fashion with operator oversight. 
The 'operational' use of this console is authorized for radio
astronomy activities under the Complex Director's discretion as
test equipment.  Testing of the Special Activities Monitor
Console should be completed by the end of next month.

     Our goal continues to be able to have astronomers at non-DSN
locations direct data acquisition in real time, to execute
automatically data acquisition scripts provided by the
astronomers, and to have astronomers remotely monitor the data
acquisition in real time.  The benefits of such a capability for
remote engineering diagnosis and testing are obvious. Experience
with remote and unattended operations, if adopted for regular
operations, has significant cost saving potential.

     The needs of the NASA SETI project, a major radio astronomy
activity, yielded the DSN rich technological harvest, which
includes wideband low-noise amplifiers and feeds, an extremely
stable down-converter, and an ultra-high resolution wideband
spectrometer.  The program also provided strong motivation for
the timely development automated and remote operations at DSS-13.


Radio astronomy provides key personnel to DSN programs

     Many astronomers have found their way into DSN-related
research and management, including Chad Edwards, Mike Klein,
Steve Lichten, Kurt Liewer, Roger Linfield, George Resch, Dave
Rogstad and Jim Ulvestad.

     Radio astronomy also has had a stimulating influence on the
work of other DSN professionals. Key personnel with other
backgrounds who have had significant involvement with radio
astronomy activities include Dan Bathker, Bob Clauss, Gerry Levy,
George Morris, Charles Stelzried, and Bob Stevens come to mind.

     Astronomers currently active in research who have or have
had beneficial influence on DSN activities are Valery Altunin,
George Downs, Dayton Jones, Ray Jurgens, Steve Levin, Victor
Migenes (CSIRO), Arthur Neill, Ed Olsen, Steve Ostro, Bill Peters
(while at ANU/MSSSO) , Bob Preston, John Reynolds (CSIRO),
Antonio Rius (UCMadrid), and Marty Slade.


                                Conclusion

     The key DSN technologies of antennas and receivers and radio
astronomy are now close to maturity, though advances which lead
to simpler operation and lower cost implementation continue to be
made.  Dramatic innovations are now coming from other
technologies, such as information management, automation, and
networking. Because of lower reliability requirements, radio
observatories are able to integrate these technologies more
quickly than the DSN.  I view the main current contribution of
radio astronomers in the DSN as being the driver for moving these
new technologies quickly into the DSN for radio astronomy
research.  Radio astronomers will accept lower reliability to
achieve performance improvement, thus giving the DSN the valuable
opportunity of evaluating and developing experience with new
technologies in non-critical operations.

     The consolidation of the Advanced Systems and Science
program offices should enhance this process.  Ideas relevant to
advanced DSN systems will continue to arise in the astronomical
community. Astronomers will generally be the first to exploit the
results of advanced systems research, providing motivation for
timely deployment and valuable experience prior to adapting them
for operational use. 

     At a time when severe budget pressures are threatening the
health of the DSN, we need to increase the rate of innovation.
Outmoded technology and techniques are expensive in maintenance
and personnel costs.  Radio astronomy can continue to initiate
and speed up the pace of innovation, resulting in a more
efficient DSN.

cc: V. I. Altunin
    R. W. Burt
    L. J. Deutsch
    S. Dolinsky
    C. D. Edwards
    S. Gulkis
    M. J. Klein
    R. A. Preston
    N. A. Renzetti
    C. T. Stelzried
    M. R. Wick