Utah MADEFAST Visit 5 July 94
This was a follow-on to the 21 Jun visit by Sam Drake and Carolyn Valiquette.

Utah MADEFAST Visit 5 July 94

Carolyn Valiquette from the University of Utah Computer Science Department visited Palo Alto and met with Sam Drake participated by phone.

Design

The design was further refined. (Note: there have been at least three local design meetings since the collaborative design meeting of 21 Jun. These were typically attended by Joe Wagner, Mark Cutkosky, George Toye, Larry Pfeffer, and Jayachandra Reddy - but are undocumented.)

Two major changes since the 21 Jun meeting was to use a component-type CCD rather than the "lipstick" camera and to eliminate the lens between two mirrors - perhaps by using a hyperparaboloid secondary mirror, with a fallback position of a flat secondary mirror. Also the local group decided definitely to use a modulated signal.

There was a general discussion of whether to go with a single or double mirror option, and if a double mirror, whether a beam splitter or mount the CCD on the back side of the secondary mirror. There was also concern with the focal length and field of view (FOV).

Sam has made the following assumptions:

The Stanford design team's estimates were different only in The Stanford design team also pushed for consideration of the single mirror option. All of these were estimates based calculations with somewhat different starting values. (Note: the FOV was decided to be +/-2-4 degrees at the 21 Jun meeting.)

Consensus was to go with 2 mirrors for a more compact design and for balance and conservation of moment of inertia. The beam splitting version will be tested to see if the signal intensity is sufficient. Mounting the CCD on the back side of the secondary has an optical (FOV) advantage.

It is an open issue still whether to use encoders or resolves and whether rate gyros can be avoided.

There was a question of whether the motor shaft diameter could be reduce and the bearings larger so they could be pre-loaded.

The design decisions and rationale are documented in more detail in the current state of the design.

Process

The State of the Process includes specific action items resulting from this meeting. General tasks and states are described below:

The Stanford team has charge of the optical design, Utah, mechanical, and both are interacting about control.

Utah will work with CMU and MSU on fabing parts. CMU may be able to make the detector shroud with SLA. MSU may make the casing with composite materials. Utah will machine everything else.

Stanford will work toward a 2 mirror design trying for a 5 degree FOV, about 50 mm height between primary and secondary mirrors, and 120-150 mm focal length. George will send Sam a sketch of the design with the CCD mounted on back of the secondary. Stanford will also test the beam splitting design.

Utah (Sam) will machine the mirrors but Mark is investigating whether Sandia Labs will also make them. Stanford will supply the geometries in any case. Joe Wagner and Jayachandra Reddy are primarily responsible.

Mark Cutkosky is leading the Stanford design team. Larry Pfeffer is primarily responsible for the control. Joe Wagner and Jayachandra Reddy are primarily responsible for optics, taking direction from Mark and Larry. George Toye is also consulting on all aspects of the design.

At the demonstration, one idea is to have "bulls eye" ring of light, modulated differently from the signal, projected in line with the CCD. Viewers would see the signal dot gradually centered in the ring. Or not. The ring can be turned off.

On the morning Wednesday the 6th, the group met and drafted a preliminary presentation outline. This will be worked on collaboratively between now and August. Larry Leifer has published these notes to the participants.

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Charles Petrie