The Secret Behind the Nobeyama 45-m
Radio Telescope’ s Excellent
Even now over 30 years after its completion in 1982, the 45 m diameter radio telescope at
NAOJ’ s Nobeyama Radio Observatory boasts world class performance for observing thecomparatively short-wavelength radio waves known as millimeter waves. Let's try to understandthe structure of the Nobeyama 45-m Radio Telescope and investigate the secrets behind its
high accuracy and sensitivity by making a paper model of this telescope.

Subreflector

Because the focal point changes as
the elevation angle of the mainreflector changes, the subreflector
moves automatically to always be at
the ideal position.

Main Reflector

The main reflector is madefrom about large 600 panels.
The deviation of the shapefrom an ideal parabola is only
about 0.2 mm across theentire surface.
The diameter is 45 m, and themaximum angular resolution is0.004 degrees (equivalent to ahuman eyesight of 4).

Collimator

There is a high accuracy telescope
called a collimator in the center part.
Because the main reflector follows
the collimator, the 700 ton giant
structure can track celestial objects
with and accuracy of 0.001 degrees.

Framework Structure of the Main
Reflector

The back structure of the Nobeyama 45-m
Radio Telescope adopts a technique called“homologous deformation method,” which is a
way to keep the surface of the telescope as
close to a paraboloid as possible, even when
the surface deforms due to its own weight.
This allows astronomers to collect radio
waves efficiently from every direction in thesky.

Bottom Equipment Compartment
and Frequency Selection Mirrors
Similar to visible light, it is possible touse a mirror to change the propagation
direction of radio waves. The radio
waves collected by the main reflector (aradio mirror) are delivered by anassembly of many mirrors to detectors
which observe different frequencies.

Main Performance Specifications
Diameter of main reflector: 45 m
Weight: about 700 tons
Mount: Altazimuth mounting
Reflector surface error: about 0.2 mm
Pointing error:
less than 4 arcseconds (about 0.001 degrees)
Observational wavelengths:
about 2 mm – 30 cm(Frequency: about 1 – 150 GHz)
Second, Third Reﬂector
Mirrors
In 2015, the second and thirdreflector mirrors inside theradio telescope wererenewed. By applying a thickgold leaf, the efficiency of theobservations increased 15%.
(The second reflector mirror
is pictured.)

FOREST ReceiverThis is the latest detector,
having opened for joint use in2015. It can perform
wide-band, 4-beam, multi-lineobservations.

Horizontal Alignment Wheels

Six wheels run along a circular railwith a diameter of 22 m, allowing
the telescope to point in any
direction, 360 degrees, horizontally.
There are 2 drive motors. It takes
about 20 minutes to revolve once inthe horizontal direction.

Receivers

In the detector room, there are various receivers forcapturing radio waves of millimeter wavelength. To
be able to detect weak radio waves, their cores arecooled to -269 ° C.
(c) NAOJ

Nobeyama 45-m Radio Telescope Paper
Model Construction Project for a Child with
Adult Assistance, Expert Course(Instructions)
Materials and tools: box cutter and glue
1. Preparation: Cut out all of the 24 components along the thick lines. Cutalong the thick lines to form incisions or holes where indicated. Mountain foldalong dot-dash lines and valley fold along dashed lines. Cut out and remove
parts marked with an X.
2. Pedestal: Make the pedestal by folding and gluing it so that it matches thephoto. Construct the two-storied bottom equipment compartment, insert itfrom under the pedestal, and glue it in place.
3. Center hub/beam transmission system/elevating equipment: Assemble
the center hub and attach the elevation axis gears to both sides. Insert theelevation axis through the upper side of pedestal and the center hub.
Assemble the beam transmission system and elevating equipment, and insert
these into the pedestal temporarily. Then carefully insert the elevation axis
into the beam transmission system (upper part) from the side and glue it.
After that, glue the elevation axis to the bottom of the pedestal.

For both themain reflector
and the Sunshield panel,
the seam isdown.

When seen fromthe front, thesub-reflector
stays form an
upside-down Y.

4. Subreflector: Attach the subreflector to the tip of the triangular prism
shaped subreflector drive. Next, glue the subreflector stays to the 3sides of the subreflector drive, enclosing it to form a tower structure.
5. Sun shield panel: Assemble the inner and outer portions of the Sunshield panel so that they form cones with the printed surfaces on theoutside. Put glue on the tabs of the outer portion and cover them fromabove with the inner portion so that they bond. Attach the main reflector
collar to the base of the Sun shield panel.
6. Main reflector panel: Assemble the inner and middle portions of themain reflector panel so that the printed surfaces are on the inside. Putglue on the tabs around the perimeter of the central hole in the outerportion and attach the middle portion. Similarly, attach the inner portion
to the inside of the middle portion.
7. Main reflector: Insert the legs of the sub-reflector stays into the 3slots in the main reflector panel and glue them from the back side. Putglue along the outer periphery of unprinted sides of the main reflector
panel and Sun shield panel, line them up, and affix them to each other.
8. Overall assembly: Attach the main reflector so that the sub-reflector
stays form an upside-down Y as seen from the front, when placed sothat the elevating equipment is on the left side. Attach the azimuth axis
rail to the base and mount the telescope.

The squarepole shaped
elevatingequipment ison the left side
as seen fromthe front.
(c) NAOJ

Subreflector drive

Subreflector stay
SubreflecLet’ s build a paper modelof the Nobeyama 45-m
Radio Telescope (1/3)
Main reflector panel(outer portion)

Sun shield panel(outer portion)

Sun shield panel(inner portion)

Main reflector panel(inner portion)

Main reflector panel(middle portion)
Main reflector
collar(c) NAOJ

Bottom equipment
compartment

Let’ s build a paper modelof the Nobeyama 45-m
Radio Telescope (2/3)
Beam transmission
system (upper part)
Elevation axis

Pedestal
Elevatingequipment

Nobeyama Radio Observatory,NAOJ45-m Radio Telescope
1/400 model
Beam transmission
system (lower part)

http://www.nro.nao.ac.jp/en/(c) NAOJ

Let’ s build a paper modelof the Nobeyama 45-m
Radio Telescope (3/3)

Center hub

Elevation axis
gear

Azimuth axis rail(c) NAOJ