The questions of antenna design with a diameter of 3 m for space radio-interferometry are examined. The basic characteristics of the antenna are determined, on the basis of which a model of the antenna of a space radiotelescope of 3.1 m KRT-3 is developed and prepared. The technological peculiarities of the antenna preparation are examined. The results of measurement of the reflecting surfaces of the telescope are cited, which point to the fact that the antenna may operate to wave lengths in the order of 2 mm

Kostenko, V. I.

Matveyenko, L. I.

English

NASA Technical Reports Server

  
 
 
N O T I C E 
 
THIS DOCUMENT HAS BEEN REPRODUCED FROM 
MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT 
CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED 
IN THE INTEREST OF MAKING AVAILABLE AS MUCH 
INFORMATION AS POSSIBLE 
https://ntrs.nasa.gov/search.jsp?R=19800003033 2020-03-21T20:51:09+00:00Z
NASA TECHNICAL MEMORANDUM
	 NASA TM -75714
ANTI. NNA OF THE SPACE RADIOTELES0OPE KRT-3
V.I. Kostenko and L.I. Matveyenko
Translation of "Antenna Kosmicheskog-o radioteleskopa KRT-3," Academy
of aciences USSR, Institute of Space Research, Moscow, Report PR-340,
1977, pp 1-20
(NASA-TM--75714) 'ANTENNA OF THE SPACE	 N80-11280
RADIOTEL'ESCOPE KRT-3 (National Aeronautics
and Space .Administration) 22 p
HC A02/MF A01	 CSCL 09C	 Unclas
G3/32 46137
r
41, y ^
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
WASHINGTON, D.C. 20546 	 NOVEN.BER 1979
s
ANTENNA OF THE SPACE RADIOTELESCOPE KRT
-3
V.T. Kostenko and L.I. Matveye.nko
Academy of Sciences USSR, Institute of Space Research
Research of the structure of quasars, cores of galaxies, pul-
	 / 3*
sars and areas of star formation is one of the most actual directions
in contemporary experimental radioastronomy. These objects or com-
pact components entering them have in some instances angular measure-
ments less than 10-3
 seconds of arc.
Reception of the detailed spacial structure of these sources
is possible only by the method of radio interferometry with the use
of a space radiotelescope.
Based on results of Soviet-American researches (1969-1976) j1)
and taking into account the possibilities of contemporary space
facilities, it is advisable to begin such studies with the objects
W49 and W51 in the water vapor line (1 = 1.35 cm). These objects
are the brightest and therefore it is sufficient to have the mirror
of the antenna of a space radiotelescope with a diameter of 3-4 meters.
Antennas for space vehicles existing at present do not fulfill
the basic requirement which is imposed for the accuracy of the reflec-
ting surface. In connection with this, the task was set forth of
creating a precision antenna for a wave of 1.35 cm. The possibility
of its operation on shorter waves is also incorporated: The antenna
must have minimal weight, work in the conditions of outer space, and
*Numbers in the margin_ indicate pagination in the original text.
1
fits diamecer must not exceed 3 M.
Technical Requirements
One of the basic elements of the space arm of a radio-interfer-
ometer is the space radiotelescope. The antenna of this radiotele-
scope must meet several contradictory requirements: have minimal dimen-
sion and weight, a high precision of sighting, but at the same time
a maximal effective surface and high precision of the reflecting;
surface.
The antenna must have the following parameters:
--working wave length of 1.35 cm;
-an effective antenna surface of no less than 4 m 2 , which with
a coefficient of antenna use of 0.5-0.6 corresponds to a mir-
ror diameter of 3 m;
--a construction weight no greater than 140 kg;
-for more effective antenna use, the provision must be made for
its use in the millimeter wave band.
Investigation of the various types of antennas has shown that it
is most expedient to use a rigid parabolic system with a Cassegrain
ian system of exposure. In this instance the apparatus may be accom-
modated in the cabin, directly adjoining the primary parabolic mir-
ror, creating a convenient arrangement of the KRT )Fig. 1). In addi-
tion, it should be relatively simple to carry out correction of error
in guidance and scan of an assigned area of the sky in the boundaries
of several beam patterns. This may be acheived by movement of a
small mirror which is particu7a.r1y attractive from an energy point
2
of view.
On the basis of study on the choice of electrical, and construc-
tion parameters, the following basic characteristics of the antenna
were determined:
	
/5_
-the primary antenna mirror - paraboloid of rotation, diameter
of 3.1 m;
-the secondary mirror - hyperboloid of rotation, diameter of
400 mm;
-focal distance of the paraboloid 1342 mm;
-focus of the hyperboloid set at a distance of 544 mm from the
focus of the paraboloid;
-exposure angle of the primary mirror 1200;
-attachment of the secondary mirror is accomplished by mountings
with a minimal shading of the antenna exposure.
Choice of the Con struction Layout of the Antenna
The peculiarity of a space rediotelescope lies in the fact that
it operates in the conditions of space (weightlessness, great drops
of temperatures), and during transport into orbit it undergoes various
forms of stress (linear, shock, and vibrational).
Upon taking these requirements into account, various variations
of construction and power systems of the antenna were examined:
-solid, frameless mirror;
-thick-walled mirror, attached to a frame;
-inflatable constructions;
-thin-walled mirror, attached to a frame.
3
Examination of the variations showed -that solid and thick-walled
mirrorek have a very great weight. The inflatable construction with
a small weight does not have the assigned precision of -the reflec-
ting surface. And only the thin-walled mirror ► attached to a rigid
frame, acheived the desired precision of the reflecting surface with
a small construction weight.
Of the three types of frames:
the first is a welded, lattice, tubular frame;
the second is a riveted cone with the assembly along the forma-
tion;
the third is a welded frame of fins and rings; u
variation I has a girder weight of the order oe 150 kg, and variations
II and III, of the order of 100 kg.
In addition, in variation I the presence of a large number of
small pieces of pipe complicates the welding of the frame and the
application of the technological fixture, and in variation II after
the assembling (riveting) of the frame and the installation of the
elements of the reflecting surface fixture, the adjustment of the
mirror is complicated.
The most prefer-01_%a seems to be variation III, which was also
accepted as the basis. In such a manner, a constructively sound
design of the antenna, shown in Fig. 2, is as follows:
-a rigid support frame;
-a thin mirror, installed on the frame;
-four supports for the installation of the secondary mirror.
4
AThe frame consists of eight large and eight small fans. The
fins are connected by three tubular rings and two rind; frame supports,
one of which is the base support for the placement of the form of the
main mirror and the cabin with the irradiating unit, and the second --
the base support for the attachment of the device network and all
of the •radiotelescope.
For the attachment of the reflecting surface; to thM.. framework
an assembly was used with supports in the form of rigid pins, shown
in Fig- 3, which was placed bath on the fins and the rings.
The reflective surface is made of eight sections of aluminum
sheets with a thickness of 1-3 mm. The supports of the secondary
mirror are four thin-walled tubes, which pivot on the other ring.
Attachment of the supports on the outer ring is the most rational 	 f7
from the point of view of acheiving minimal shading of the antenna.
The secondary mirror is a rigid hyperboloid of rotation.
With the goal of providing for minimal construction weight of
the rad-4 otelescope and the technology of its construction, the base
materials selected were aluminum and aluminum alloys (type AD-1, AMg
and AM).
rreparation of the Antenna Model for the KRT-3
For the preparation of an electric model of the Irojected anten-
na, the technology of its preparation during experimental manufac-
ture was formulated.
The entire process was broken down into the following sta!ess
5
-preparation of the frames
-preparation of the molds of the parabolic and hyperbolic mirrors;
-preparation of the matrix for the formation of the surface of
the parabola,
-installation and adjustment of the reflecting surface of the
primary mirror.
The mold of the primary mirror is intended for the placement of
the supports of the reflecting surface, the implementation of the
mirror adjustment and is used in the preparation of the matrix for
the formation of the parabolic surface. The basic working surface of
the mold is a blade made of a sheet of steel Kh18N9T with a thickness
of 2 mm. The working edge is made with a precision of + 0.05 mm (max-
imal tolerance deviation from the profile of the calculated parabo-
loid). The blade of the mold is inserted into a fin, constituted of
a packet of sheets which is attached to the rotating collar. The col-
lar terminates with a disc 9 500 mm for the attachment of the mold to
the base ring of the frame.
The mold allows for placement of the support for attachment of
the antenna mirror relative to its edge with a precision of + 0.05 mm. /F3
The adjustment of the reflecting surface is carried out with
the help of clockwork indicators which are additionally attached to
the blade of the mold.
The mold-copy of the secondary mirror is intended for the pre-
paration of the hyperboloid on a lathe- or lathe-copying device and
is plastic with a thickness of 5-10 mm with a profile of the hyper-
6
boloid turned on it. The precision of the completed profile is + 0.02
mm.
For the formation of the reflecting; surface, special equipment
was designed and prepared which incorporates a 3haped cement founda-
tion in a trough and a roller with a welpht of 160 kf-, , which has a
surface precision of + 0.5 mm.
rrecision of the Surfaces
Attachment of the reflecting ourface of the primary mirror was
accomplished at 1248 points. The position of these points, after the
adjustment was done, was also measured. The results of the measure-
ment are shown in Fig. 4.
The maximal error of the profile consisted of ± 0.1 mm. The root-
mean-square error of deviation of the actual paraboloid at an assigned
point from the theoretical equals
•+- 0.066mm
n -1
Thus the results of the measurement of the reflecting; surface
of the paraboloid allow one to make deductions about the accuracy of
the chosen construction, the technology of preparation and method
of adjustment, which allows for the creation of an antenna mirror
with a surface precision no worse than + 0.1 mm.
The prepared mold-copy of the secondary mirror and the hyper-
boloid itself were measured with the aid of a clockwork indicator of
0.01 mm on a coordinate-borer, type 2V440A with a step of 3 mm along /9
the radius (at 68 points). Charts of the measurement of the mold-
7
a.
copy and the hyperboloid are shown in Fib. 5.
The maximal error of the profile of the hyperbol,oid consists
of + 0.05 mm.
The Ex Pected Coefficient of Surface Use
In a general case when the distribution of surface areas conforms
to the normal law and the representative measurement of discontinui-
ties at the surface of the mirror is significantly less than its
aperture, the coefficients of use of the actual and ideal antenna with
even exposure are connected by the relation [23
PA /
nnAo 
= ex  (- ^ ) m
!
Then, substituting in this relation the value 5, we receive
'%/ I Ao = 0.995 and 'Z A/ j Ao = 0.840 for waves of 1.35 and 0.2 cm
respectively. Consequently, with the accepted assumption, the loss
of effectiveness for waves > 2 mm does not exceed N 15%.
For actual exposure of the antenna and the received errors of
the surface, the value of the effectiveness of the area may be made
in the following assumption.
Let tho element of the surface be the area
,A5=5A@RL = 0.655RL
where A.9=  0.131 rad is the angular aperture of the element with a
length of 5 cm.
The deviation of this element from the theoretical position of
the paraboloid at a value of ± A? is accepted in the direction of
8
the normal to the surfaca. In this case the change of phase equals
2:7,^ ^t +Ca,^ cp^
a ^'
In addition, the contribution of each element of the surface
	
/o
to the effective area of the antenna depends on the form of distri-
bution of the field in the aperture of the paraboloid. Two types of
the form of distribution were examinedt
a) the law of mode distribution
=Eocos fi
where ,^ = 'Fw ith R = 15!)0 mm;
b) distribution of the field with a 10o overexpnsure
(R)23P
where 'X is the level of exposure of the edge; ge = 0.1;
5) is the actual value of the radius, and t = 1.
Henoe
A(	 0.9(R)2.
Finally, with the determination of the actual effective area of
the antenna, each element of the surface introduces a contribution
to the energy flow, which is proportional. to
L	 ^^,^.	
9	
a
^	 R2 r
The results of the calculation of antenna effectiveness by the
derived method are shown in Figs. 6-8. As follows from these data, the
actual errors in the preparation of the surface of the KRT-3 give
9
rise to effectiveness loss of no more than 10,Z for waves	 2 mm.
/I:^Oncluaion
Thus the der
method of design,
a space telescope
a diameter of 3-4
band.
Ived results attost to the fact that the sumlpested
preparation and adjustment of rigid mirrors for
permits the creation of precision antennas with
m which work effectively in the millimeter wave
Ak
Performance of terrestrial experiments in the future will allow
for the determination of the electrodynamic characteristics of the
antenna and to make deductions about the interaction of electrical
and mechanical parameters of mirrors of a given type.
The authors consider it Cheir pleasant suty to express thanks
to A.Y. Bor-Ramenskiyj L.I. Volkov, M.I. Grigor l yeva, G.N. Khramov
and V.N. Shchepem l yev who took an active part in the creation of the
antenna.
REFERENCES
1. Batchelor, R. Dzhonsi, D.L., Dzhonstonp K.D.s Efanov i V#A* ►
Kootenkop V.I. Matvayenko, L.I., Moiseyev i I.G.j Noils, S,KH.,
eapatoonko, A.M., Prooton, R,j Spenser, D., Timofeyev, A#Nsj
Fourikio ► ► .F., Shilitoi t R-Xbil-p "llic'ma v Astronomicheskiy
Zhurnal"p T. 2, No. 10 ► 467 PP., 1976,
2. Ruze ► T• ► L)rqp.-. I@EaBsEi p volt L4 1 i). 633o 1966,
11
0
Vi
}-1
C)0
0 3I60
Figure 1. Layout of the radiotelescope.
12
Figure 2.
13
fFigure 3. "1eme.nts of reflecti
surface a'.-tachment .
14
I1 S	 ADOUT F
I 
a-Iq
17JU
Nm
Designation of errors
4	 rj
WA	 m M
0 +0 05	 mm
13	 +0.1 mm,
Ix	
0	 —0 " 0
-
5 mm
A,& --0 1 05>6,-, -0 - mm,
mm.
Y11
7
Field y,/U'<o
Field w/ =0
TJ5 0
--_,11-^ield w/ 6>0
7
vi
10wour MAWN
-PD-7
A"'
Figure 4. Chart of measurement of the
model KRT
-3 antenna mirror.
16
Y^
O^
1^0(1"1
^W^
P4
b
rd
O
CH
0
co
+--1
a>
a^
cd(1)
rz
0
p
cd4U
Vl
a)
4A
+riI	 rt4
	 I
17
-,W.,•
O	 pt,7
	 co	 p	 F LID
I
a^
410
0
rOr,f'1
/A
W it
4.3
CH
O^p
0o
4
ti
W
Z
E
O
4-I
CHH
^
0
JW
.
rH.
4-4
[O[,
p
A
a)
v
4a
0
p
0
0"
CH 0
(D p
.0 0
-P$^4z';,
0
.d v
v
4-) ^4
0
CH
vv
^N
C0 v
^ N
v
^ ^H
4 ^^
U N U
CH
v 0a
v ^
.^ v
w 0
0
v 0.
U ,r{
N •^1
a-P
v cn
ra
b
N fU
^^^^  T
"r{ CH
rT1 0
+;
^	 Qi
18
r
r—I
rz
as
P4
0
Cd
-P
CH0
a)
od
(1)
^4V
,.4{
4-1
0
.p
r4-i
CH
14
b.0
CH CH
cl)
cn
19
C^
.r-f
$4
0
f4
ii
C^
4-^
r_
Cd
E-4
a)
4-1
0
Cd4-^
0
0 4-3
a) bD
CH
CH 
r^
(1)
bO
1^4
4-q p
0 0
40
0 0
00 r.
0
P 4-1
::s Cd
^
v
T
E:
F.:
A.
4-1
20
4 .
Lia^_


Antenna of the space radiotelescope KRT-3

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server