South Pole Telescope Design
8 December 2003

South Pole Telescope Design

This website describes optical design work on the South Pole telescope.

The South Pole telescope optics have these design criteria:

1. 8 meter diameter primary with 1 meter shield---in the optical design, this is represented by a 10 meter diameter primary.
2. All apertures are unblocked.
3. All optical elements are reflectors, with the exception of the dewar window.
4. Dewar window must be a manageable size
5. Chopper mirror is near image of primary mirror
6. An image of the primary is available at a cold point inside the dewar, for use as a Lyot stop
7. Illumination of primary extends to 3.5 meters radius from center
8. Image has 1000 beams within 20 cm diameter

SPST67 a simple design, but inconvenient placement of detector

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 element

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 primary.

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.

This page was last updated on 12/08/03.