Cover story: secrets of high accuracy of

ASTE 10m antenna

The ASTE Telescope observes radio wave with the wavelength of
1mm or shorter (submillimeter wave). The antenna has very highperformance - for instance, each antenna has a surface accuracy
better than 20 um (root mean square). Let us learn the reason why
these antennas can achieve so hight performance, by making a scalemodel of the ASTE 10m antenna.

Specifications of the ASTE 10m antenna
Antenna diameter
WeightSurface error
Pointing error

10 m90 tons
20 um or less
0.6 arcsec(1/6000 deg) or lessObserving frequency

30-950 GHz(10-0.3 mm om wavelength)
Maximum drive speed 6deg/sec (azimuth)
3deg/sec (elevation)
MountAlt-azimuth

Subreflector stayis thin enough so thatblocking are minimized

Sunshade
Subreflector

prevents thermal distortionof main reflector and backup
structure due to sunshine

Backup structure:

is made of CFRP andinvar so that gravitational
and thermal distortions
are minimized

Receiver cabin

contains very highsensitivity receivers

Main refrector

consists of 205 panels,
each having an accuracy
better than 5 um (rms),
whose relative positions
are measured andadjusted by using radio
holography method.

Elevation axis

Optical pointing telescope

Azimuth gear

drives azimuth of
the antenna at very
high accuracy

Sector gear

drives elevation of
the antenna at very
high accuracy
Photo: Kouichiro Nakanishi (NAOJ)

Photo: Kouichiro Nakanishi (NAOJ)

Designed bs Seiihi Sakamoso (NAOJ)(c) National Astronomical Observatory of Japan

Lets build a paper model of

ASTE 10 m antennabarrel. Glue the subreflector on one end of the subreflector mount.
Glue the subreflector stay to form an apex. Attach the subreflector
mount to the center of the subreflector stay.

Tools & material: art knife, ruler, needle, white glue, coins, toothpick

5. Form two cones with inner and outer rings of sunshields so thatthe printing faces outside. Attach the two cones into one.

0. Copy the parts sheets onto white card stock so that the outer
frame forms a 18 cm x 26.5 cm rectangle.

6. Form a cone with outer ring of main reflector so that the printing
faces inside. Attach the inner ring to the outer ring from the inside.

1. Cut out all 11 parts from the parts sheets along thick lines. Remove
holes surrounded by thick lines. Score and fold backwards (mountainfold) along chain double-dashed lines. Score and fold forwards(valley fold) along dashed lines.

7. Insert the ends of the subreflector stay into the holes on the mainreflector surface and glue from the rear side. Glue the outermost
ends of the main reflector surface and the sunshield and assemble
into one piece.

2. Glue and form the york so that it shapes like a tuning fork.

8. Fix the york on the foundation in a manner that the flat side of theyork is facing the front side. Mount the receiver cabin to the york witha toothpick in a manner that the larger end of the cabin is in the backside. Attach the main reflector to the + mark of the receiver cabin in amanner that the subreflector stay is X-shaped when seen from thefront side.

3. Attach quarter coins to the backside of themark as a balance
weight, and assemble the box. Glue the sector gear along the linethat goes though themark.
4. Roll up and glue the subreflector mount to form a 4 mm diameter

Subreflector staylooks X-shaped
when seen fromthe front side.
Flat side of
the york faces
the front side.

Larger end of
the cabin is in
the back side.

(c) National Astronomical Observatory of Japan

Let's build a paper model ofReceiver cabin

ASTE 10m antenna

ASTE 10m antenna
1/100 scale modelYork

http://alma.mtk.nao.ac.jp/aste/index_e.html

Foundation

Glue and roll up

Subreflector mount

Subreflector stay

Subreflector(c) National Astronomical Observatory of Japan

Let's build a paper model ofSunshade (outer)

ASTE 10m antenna

Main reflector (inner)

Sunshade(inner)

Sector gear

Main reflector (outer)(c) National Astronomical Observatory of Japan