A 2.3 GHz traveling-wave maser/closed-cycle refrigeration system was installed on the 64 m antenna at Usuda, Japan. This was done to evaluate the beam-waveguide antenna noise performance, and to support the International Cometary Explorer's (ICE's) comet flyby mission. System noise temperature at 2270 MHz was measured to be 15 K, including the maser noise contribution of 2.5 K. Maser installation and noise performance are described. The Usuda 64 m antenna is of high quality with a system operating noise temperature better than the DSN 64 m antennas

Neff, D.

English

NASA Technical Reports Server

N81-23831 
TDA Progress Report 42-89 January-March 1987 
Use of a 2.3-GHz Traveling-Wave Maser on the 
Usuda 64-Meter Antenna 
D. Neff 
Radio Frequency and Microwave Subsystems Section 
A 2.3-GHz traveling-wave maserlclosed-cycle refrigeration system was installed on the 
64-m antenna at Usuda, Japan. This was done to evaluate the beam-waveguide antenna 
noise performance, and to support the International Cometary Explorer's (ICE 's) comet 
jlyby mission. System noise temperature at 2270 MHz was measured to be 15 K ,  includ- 
ing the maser noise contribution of 2.5 K. Maser installation and noise performance are 
described. The Usuda 64-m antenna is of high quality with a system operating noise tem- 
perature better than the DSN 64-m antennas. 
1. Introduction 
The Institute of Space and Astronautical Science (ISAS), a 
Japanese agency that is similar in function to NASA, com- 
pleted construction of a 64-m cassegrain antenna in October 
1984 at Usuda, Japan, approximately 180 km west of Tokyo. 
This antenna is a more modern design than the DSN 64-m 
antennas, the first of which was completed in 1966. The 
Usuda antenna uses shaped main and subreflector surfaces, a 
beam-waveguide feed system, automatic subreflector position- 
ing, extensive digital control systems, very modern receiver 
equipment with fiber optics interface to the antenna, and 
automated station control with remote monitor and control 
capabilities from Tokyo. 
NASA's interest in the antenna's beam-waveguide noise 
temperature performance and a decision to use the antenna 
for tracking the International Cometary Explorer (ICE) [ l ]  
prompted an agreement to ship, install, and operate a 2.3-GHz 
traveling-wave maser (TWM) and closed-cycle refrigerator 
(CCR) system to support the ICE Giacobini-Zinner comet 
flyby. This article describes the preparation, installation, test- 
ing, and operation of the TWM-CCR system in support of 
these objectives. 
II. Preparation 
Starting in August 1984, new equipment was ordered and 
existing equipment was assembled for the planned TWM-CCR 
installation at Usuda. The equipment required for the installa- 
tion, operation, and maintenance of the system had to be sup- 
plied from JPL to the site. A TWM developed in 1973 [2] was 
available, as well as a compressor and helium purifier from the 
JPL and DSN inventory. The balance of the system was bor- 
rowed from several other projects to reduce costs (all equip- 
ment was returned to IPL when the task was completed). The 
TWM was tested at JPL on the roof of Building 238 in March 
1984, and the results were virtually identical with the noise 
data taken in 1974 at 2295 MHz (Table 1). The total system 
noise operating temperature (Top ), measured at 2270 MHz 
(10.2 K), was quite acceptable, so the TWM components 
were shipped in March 1985 via air freight. 
34 
https://ntrs.nasa.gov/search.jsp?R=19870014398 2020-03-20T10:26:35+00:00Z
111. Site 
The antenna (Fig. 1) is located in a forest preserve on the 
side of a mountain at a 1074-m elevation (N = 36'07'49", 
E = 138'22'03"), approximately 15 km from the town of 
Usuda in the Nagano prefecture. Standard access to Usuda 
is by train via Komora from Tokyo Ueno Station. Travel 
time is 3 to 4 hours, depending on transfer connections at 
Komora. Equipment must be transported by truck from 
Narita Airport (80 km west of Tokyo) over generally good 
roads. The last 8 km are over a maintained dirt road. Access 
in the winter is sporadic due to heavy snow at various times. 
Rain is a common occurrence the rest of the year and varies 
from clouds and mist to heavy precipitation. A dormitory 
building has recently been completed to reduce travel require- 
ments for personnel working at the site. 
V. Problems 
Maser testing at the site was delayed a week because of a 
CCR warm-up problem during the test period allocated by 
MELCO. The station ran on a rather fixed and predetermined 
schedule because of the ongoing antenna work and acceptance 
testing being performed by MELCO. The TWM system testing 
was later restricted to  brief periods before and after actual 
tracking periods. 
IV. Installation and Layout 
Mitsubishi Electric Company (MELCO) installed a 2.3-GHz 
feedhorn in a low-noise configuration for use with a TWM 
(Fig. 2). The antenna feedhorn, complete with polarizer 
and orthomode transducer, terminates in an air-conditioned 
room, allowing easy access to equipment. The maser equip- 
ment rack (Fig. 2) was located adjacent to the maser, requir- 
ing only a 3-m cable run. The compressor is in another room 
where temperatures can vary between -2OOC and above 35OC 
(Fig. 3). Earthquakes are a constant threat in Japan, and 
therefore everything was braced and securely bolted in place 
to the antenna structure. 
A block diagram of the antenna microwave front end and 
TWM system is shown in Fig. 4. The front end consists of the 
following: 
Main 64-m shaped surface 
Shaped cassegrain subreflector 
Four beam waveguide reflecting surfaces [ l ]  
S-band antenna feedhorn 
RCP/LCP orthomode polarizer 
WR 430 waveguide switch 
WR 430 waveguide 
33-dB directional coupler 
TWN/CCR assembly 
The beam-waveguide system uses a movable mirror as a 
switch to connect to other feeds. A separate feedhorn with 
angle tracking and diplexed transmitter and receiving ability 
can be used for two-way communications with spacecraft at 
S-band. 
The TWM experienced warm-up problems about every 4 to  
6 days when first installed. Troubleshooting was difficult 
because the station was not manned 24 hours a day and 
failures often occurred during the night. The warm-up prob- 
lems were believed to be caused by helium gas contamination, 
either from the compressor or from the helium supply source. 
The helium gas purity at the station was checked and found 
to be at least 99.999 percent pure. It was next suspected that 
the problem might be associated with the CCR drive cylinder 
system. The drive was changed with no improvement. Fin- 
ally, the helium compressor was replaced with a spare unit. 
This contamination problem was not observed again, and the 
TWM operated normally during tracking periods for the ICE 
spacecraft. The suspect compressor was returned to JPL, 
where it was found to exhibit the same symptoms with a sec- 
ond refrigerator as those observed at Usuda. This compressor 
has subsequently been found to have an oil breakdown prob- 
lem not observed in other compressors. The exact failure 
mechanism is not yet known, but an overheated component 
in the 440 three-phase motor or head assembly is suspected. 
VI. Test Results 
The first Top measurement was made on April 29, 1985 
using the cold sky/ambient load Y-factor technique. During 
clear sky conditions with the antenna at zenith, Top mea- 
sured 15.7 K at 2270 MHz and 15.0 K at 2295 MHz. After 
additional TWM tuning experience was obtained at Usuda, 
Top final measurements of 15.0 K at 2270 MHz and 15.0 K 
at 2295 MHz were obtained. The net maser gain was between 
45 and 50 dB, and instantaneous bandwidth (at -3 dB points) 
was approximately 20 MHz. 
A tipping curve from 10-deg elevation to zenith was made 
and is plotted in Fig. 5. Data from a typical DSN antenna is 
shown for comparison. The subreflector support is a tripod 
rather than the quadripod structure used in the DSN and 
results in less blockage and lower ground noise. The improved 
noise performance, compared to the DSN data, varies from 
1.5 K at the zenith to 4.5 k at the 10-deg elevation angle. 
The system noise temperature performance comparison 
between an existing operational DSN S-band antenna and the 
Usuda antenna is shown in Table 2 (from [ 11 ). 
35 
VII. Beam-Waveguide System 
The fact that the system noise temperature remained nor= 
mal during heavy rain and did not increase is due to the design 
of the beam-waveguide system, since the horn window is pro- 
tected from rain and is heated to prevent water condensation. 
The beam-waveguide system (shown in [ 11 ) consists of an 
approximately 3.5-meter-diameter tube with the necessary 
reflectors to refocus the microwave energy to the feedhorn. 
The feedhorn is a Potter dual mode sheet metal type [3], and 
is about 7 meters in length. The length (which is about twice 
that of DSN feedhorns) is required to reduce phase error at 
the horn aperture-a requirement of the beam waveguide sys- 
tem. The antenna in its present configuration has provisions 
for other antenna feedhorns, either at the same frequency or 
at other frequencies. 
VIII. Summary 
The ISAS Usuda 64-m antenna is a modern beam-waveguide 
antenna of superb quality with operating noise temperature 
performance better than the DSN 64-m antennas. The most 
outstanding feature from a hardware point of view is the 
ability to quickly install and maintain large pieces of equip- 
ment. The beam waveguide allows flexibility for multiple 
feed systems, multiple frequency bands, and expansion for 
future programs without compromising the performance of 
any existing front end system. 
All goals of the ICE Giacobini-Zinner comet encounter 
involving the installation of the 2.3-GHz TWM were met, 
and much was learned about the new ISAS 64-m antenna. 
Future DSN antenna construction should consider the features 
and merits of the Japanese design. 
Acknowledgment 
The author would like to acknowledge the many people at Usuda for their help, 
cooperation, and patience, particularly Dr. T. Nishimura and Dr. T. Takano for making 
things happen, often under a very difficult schedule. Special thanks are due Clarence 
Hoynes and Richard Spear for their help in troubleshooting and repairing the TWM, 
and to Mike Britcliffe for diagnosing and correcting the problems with the cryogenic 
system. Thanks also to R. Clauss for performing the tipping curve comparison and his 
many helpful discussions. 
Ref e rences 
[ l ]  J. P. Goodwin, “Usuda Deep Space Center Support for ICE,” TDA Progress Report 
42-84, October-December 1985, pp. 186-196, Jet Propulsion Laboratory, Pasadena, 
Calif., February 15, 1986. 
[2] R. Clauss and E. Wiebe, “Low-Noise Receivers: Microwave Maser Development,” 
JPL Technical Report 32-1526, Vol, XIX, November-December 1973, pp. 93-99, 
Jet Propulsion Laboratory, Pasadena, Calif., February 15,1974. 
[3] P. D. Potter, “A New Horn Antenna with Suppressed Sidelobes and Equal Beam- 
widths,”Microwave Journal, Vol. 6, pp. 71-78, 1963. 
Table. 1. The comparison of system noise temperatures 
Top, Switch 
Coupler, K 
Frequency, MHz Top, K TWM, K and Year 
2295 8.3 2.1 N/A 1974 
2295 8.3 2.2 8.5 1985 
2270 9.1 3 .0 10.2 1985 
Table 2. System comparison 
Components 
DSS 14, K *  Usuda, K* 
Zenith 30-deg Elevation Zenith 30-deg Elevation 
TWM 
Feed Components? 
Antenna (spillover) 
2.5 
4.4 
4.5 
Sky (cosmic + atmos.) 4.6 
Totals 16.0 
2.5 
4.4 
6.7 
6.5 
20.1 
2.5 
3.9 
4 .O 
4.6 
15.0 
2.5 
3.9 
4.9 
6.5 
17.8 
*Low-noise configuration, 2295 MHz. 
t Feed components at DSS 14 include: calibration coupler, switch, transmit filter, orothomode junction, polarizer, rotary joints, 
feedhorn and two reflex feed reflectors. Feed componets at Usuda include: calibration coupler, switch, orothomode 
junction, polarizer, moder generator, feedhorn, and four beam-waveguide reflectors. 
37 
Fig. 1. Usuda antenna 
Fig. 3. Compressor room 
Fig. 2. Maser and instrumentation equipment 
38 
MAIN 64 meter A- REF LECTOR \. ,I 
FLAT PLATE 
REF LECTORS 
TlON 
TEST PORT 
FREQUENCY 
COUPLER METER COUPLER 
SIGNAL 
GENE RAT0 R 
2.2-2.4 GHz 
WAVEGUIDE r 2 POSITION PLATE 
AMBIENT ORTHO- 
JUNCTION 
1 H WAVEGUIDE INPUT 
1. STATION REFERENCE SIGNAL TERMINATION ::ELER I- 2. MASER TEST SIGNAL 
I 3. NOISEDIODE 
I OUTPUT FOR 
ISOLATOR 
2.5 GHz 
LOW PASS 
FILTER 
Top MEASUREMENTS 
TUNABLE 
FILTER 
2.2-2.5 GHz 
1 I ISOLATOR I 
+24 dB 
AMPLl F I E R HYBRID I SO LATO R 
ISOLATOR 
OUTPUT TO 
STATION 
RECEIVER 
Fig. 4. RF block diagram 
39 
LU 
15 - 
10 - 
5 -  
I I I I I 
USUDA 64-IT 
01 
0 10 12 15 20 30 60 
ELEVATION ANGLE, deg 
Fig. 5. Tipping curve 
40 


Use of a 2.3-GHz traveling-wave maser on the Usuda 64-meter antenna

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