A 2.3 GHz traveling-wave maser/closed-cycle refrigerator (TWM/CCR) that is used in the DSN was installed and successfully operated on the 64 m antenna at Usuda, Japan. The TWM/CCR supported the first very long baseline interferometry (VLBI) experiment to use an orbiting spacecraft as one of the receiving antennas. The experiment required a 15 K receiving system over a 2271 to 2285 MHz bandwidth. The maser installation was made during June 1986, and successful VLBI measurements were made during July and August 1986 and again in January 1987

Quinn, R. B.

English

NASA Technical Reports Server

TDA ProgressReport42°92
N88-18779 i
Octo_r-Oecem_rl_7
A 2.3-GHz Maser at Usuda, Japan, for TDRSS-Orbiting
VLBI Experiment
R. B. Quinn
Radio Frequency and Microwave Subsystems Section
A 2.3-GHz traveling-wave maser/closed-cycle refrigerator (TICM/CCR) that is used in
the DSN was installed and successfully operated on the 64-m antenna at Usuda, Japan.
The TWM/CCR supported the first very long baseline interferometry ( VLB1} experiment
to use an orbiting spacecraft as one of the receiving antennas. The experiment required
a 15-K receiving system over a 2271- to 2285-MHz bandwidth. The maser installation was
made during June 1986, and successful VLB1 measurements were made during July and
August 1986 and again in January 1987.
I. Introduction
A request was made to the Radio Frequency and Microwave
Subsystems Section at JPL to install and operate a traveling-
wave maser/closed-cycle refrigerator (TWM/CCR) on the 64-
meter antenna at the Usuda Deep Space Center (UDSC) near
Usuda, Japan. The 15-K receiving system was required for the
conceptual demonstration of a very long baseline interferom-
etry (VLBI) experiment that uses an orbiting receiving station
at one end of the baseline [1], [2]. The TWM/CCR was pre-
viously used at Usuda for the tracking of the International
Cometary Explorer (ICE) during the comet flyby period in
1985. This previous maser system installation has been thor-
oughly described in [3], so a detailed description will not be
repeated here. Although the maser system was similar to the
first implementation, modifications were made to improve its
operation and reliability.
II. TWM/CCR
The TWM/CCR was originally built and implemented in
the DSN in 1973 and was one of the first 2.3-GHz masers to
use the cold probe type of low-noise cryogenically cooled
input transmission line [4]. Due to the age of the system and
the amount of shipping and handling to which it had been
exposed, it was felt necessary to open the CCR and make the
desired corrections and improvements.
The signal input impedance match had degraded consider-
ably in relation to its original performance. The input return
loss Was increased to 13 dB at 2270 MHz and 17.5 dB at
2300 MHz, a 3- to 4-dB improvement, by replacing and tun-
ing a short section of coax in which there had been a slight
migration of the Teflon dielectric. No changes were made to
the maser structure itself.
The shock and vibration that had occurred during previous
shipping had caused some hardware to become loose. Most
notable were the screws that attach the thermal switch. A
loose connection at this point causes a poor thermal contact
and results in a longer maser cool-down period. The problem
was attributed to rotational loads that could be applied to the
joint during shipping, coupled with the soft copper material
involved. An additional structural brace made of thin-wall
4O
https://ntrs.nasa.gov/search.jsp?R=19880009395 2020-03-20T08:21:45+00:00Z
stainless steel tubing has been installed on two masers to date,
and the problem has not recurred in the last 2 years.
New cryogenic temperature sensors were installed on the
refrigerator, and the CCR controller in the instrumentation
rack was modified to provide digital readout capability for the
sensors. These sensors provide a continuous, accurate readout
of refrigerator temperatures, enabling more accurate diagnosis
of refrigerator performance problems than was previously pos-
sible. Identical sensors are now being installed in DSN maser
systems.
III. Shipping, Installation, and Operation
The experience gained during the shipment of the TWM/
CCR to Japan in 1985 helped prevent many of the problems
that can occur due to the complexities of foreign customs
policies. With this information available, it was possible to
predict and eliminate all of the previous delays, and the sys-
tem arrived in Usuda 8 days after its shipment from Los
Angeles International Airport.
The beam-waveguide feed configuration of the Usuda an-
tenna greatly contributed to the ease of installation of the
TWM/CCR. Since most of the mounting hardware had been
left in place in the laboratory environment of the beam-
waveguide antenna, minimal problems or delays were encoun-
tered during installation. Whereas installation in a DSN Casse-
grainian antenna requires advance s.cheduling of an 8-hour
maintenance period, installation of the TWM/CCR system was
completed and the cryogenics were ready to start one day
after its arrival, with no interruption of ongoing tracking
activities or maintenance.
The initial operation of the system was not without prob-
lems. One compressor and a CCR drive unit were replaced dur-
ing the first week. After that, the maser continued to be opera-
tional without further mishaps during the 1-month-long
TDRSS experiment 1986 observing schedule. In January 1987,
during the second phase of the experiment, the TWM/CCR was
easily restarted and operated without difficulty during the
lO-day 1987 observing schedule.
The maser was tuned to 2277 MHz, and the initial system
gain and power levels were adjusted: System temperature mea-
surements were first made on July 3, 1986. The gain was
adjusted to 50 dB with a bandwidth of approximately 20 MHz
at the -3 dB points. Using the cold sky/ambient load Y-factor
method, the system noise temperature was measured to be
14.9 K at an antenna elevation of 90 degrees. During January
1987, the maser gain was adjusted to 48 dB at a bandwidth of
approximately 25 MHz. The system temperature was mea-
sured to be 15 K. This performance was essentially identical
to data taken in 1985 for the ICE installation, when system
noise temperature measured 15 K at 2270 and 2295 MHz.
IV. Conclusion
For the second time in as many years, a complete TWM/
CCR system was shipped and installed on a foreign antenna in
a timely manner. The project was a relatively cost-effective
one, since it largely involved preexisting hardware. The TWM/
CCR system performed reliably without the benefit of an
operational spare and contributed to the success of the VLBI
experiment it supported. The beam-waveguide feed configura-
tion of the Usuda 64-m antenna, in contrast to the DSN Casse-
grainian antennas, also contributed to ease of installation and
operation.
41
Acknowledgments
The author wishes to express gratitude to the many people who made possible the
success of this project. In particular, thanks are due to M. Britcliffe, whose knowledge
and help in the timely diagnosis and correction of the initial cryogenic problems were
indispensable, and to D. Neff, who was responsible for the previous installation and who
furnished much help and guidance. Thanks also to L. Weight and his group for the pack-
ing and transportation between JPL and Usuda, and to R. Tanaka and his crew from
Keihin.Burlington for their work in unpacking, repacking, and transporting the system
within Japan. Special thanks to the many people from ISAS and UDSC for their help and
cooperation in making the project a success.
References
[1] G. Levy et al., "Very Long Baseline Interferometric Observations Made With an
Orbiting Radio Telescope," Science, vol. 234, pp. 187-189, October 10, 1986.
[2] J. S. Ulvestad et al., "Very Long Baseline Interferometry Using a Radio Telescope
in Earth Orbit," TDA Progress Report 42-88, vol. October-December 1987, Jet
Propulsion Laboratory, Pasadena, California, pp. 1-10, February 15, 1987.
[3] D. Neff, "Use of a 2.3-GHz Traveling-Wave Maser on the Usuda 64-Meter Antenna,"
TDA Progress Report 42-89, vol. January-March 1987, Jet Propulsion Laboratory,
Pasadena, California, pp. 34-40, May 15, 1987.
[4] R. Clauss and E. Weibe, Low-Noise Receivers: Microwave Maser Development,
JPL Technical Report 32-1526, vol. XIX, November-December 1973, Jet Propul-
sion Laboratory, Pasadena, California, pp. 93-99, February 15, 1974.
42


A 2.3-GHz maser at Usuda, Japan, for TDRSS-orbiting VLBI experiment

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server