- 8 meter diameter primary with 1 meter shield---in the optical design,
this is represented by a 10 meter diameter primary.
- All apertures are unblocked.
- All optical elements are reflectors, with the exception of the dewar
- Dewar window must be a manageable size
- Chopper mirror is near image of primary mirror
- An image of the primary is available at a cold point inside the dewar,
for use as a Lyot stop
- Illumination of primary extends to 3.5 meters radius from center
- Image has 1000 beams within 20 cm diameter
SPST67 a simple design, but inconvenient placement
SPST129 a variant on SPST67, where the detector
is moved by insertion of a nearly-flat mirror
SPST148 attempt to simplify dewar---only one
mirror inside dewar, but no place for Lyot stop, and it may be impossible to
baffle detector from window.
SPST152 add two mirrors to SPST148 to try to
create position for Lyot stop and filters.
SPST183 uses a cold silicon lens as the final
SPST208 has four warm mirrors and a cold lens
after chopper. This design has some problems which have been improved
upon in subsequent, similar designs. Lens is 400 mm diameter, Lyot stop
is 170 mm diameter.
SPST271 is an attempt to reduce the number of
mirrors. This design produces (possibly) acceptable results for a 2mm
wavelength system over a reduced field of view (0.4 degree diameter) using two
mirrors and a lens after the chopper.
SPST298 is a no-chopper design with Lyot stop.
The secondary and tertiary are shaped. The tertiary is sufficently flat
that it may work as a chopper, although it is a long way from the image of the
SPST304 is a no-chopper design with detector
placed closer to azimuth axis. Detector can be moved more in z
direction, but mirrors will get large. Secondary is shaped.
SPST307 is a shaped-secondary design with
chopper at image of primary. Well-corrected, but placement of dewar is
awkward. Only 5 mirrors.
SPST313 is a shaped-secondary design that has it
all-chopper at image of primary, high-quality Lyot stop, adequate correction
over entire field of view. Six mirrors.
SPST320 is also a shaped secondary design with
two possible configurations--- one with a chopper and one without.
SPST342 is an exercise where the chopper is
pulled back from the secondary to allow clearance. The effect on the
illumination of the primary and secondary is considered as a function of
chopper angle. This model has a plastic lens instead of silicon.
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