# Gigacam R&D

There are three development areas and one research area related to the
physical packaging of the optical imager. The development areas are a
concept for the CCD mount, the mounting of the CCDs into a focal plane
array, and a thermal/particle shield for the array. The research area is
to establish procedures for on-orbit calibration and performance
tracking of the focal plane array.

Mass and moments of the focal plane array and its shield need to be
estimated to feed into the overall spacecraft design. The size of heat
radiator is driven by the thermal load, both black body and electrical,
on the focal plane. An interface between the focal plane and the
radiator needs to be conceptualized.

Calibration needs will impact the observation program and support
equipment may need to be located within other components of the
spacecraft.

The R&D tasks described below are

-   Develop concepts.

-   Prototype concepts.

-   Build small system concept prototype.

-   Develop calibration procedures.

-   CD1 planning.

## Develop concepts

This set of activities develops our concepts for packaging CCDs into
modules, populating a focal plane array with these modules, cooling the
array, and shielding it from thermal and particle backgrounds.

### CCD mount

We want a CCD package that is four-side abuttable so that a densely
packed focal plane array with small dead space can be populated. The
package needs to provide mechanical and thermal attachment to the array
cold plate and to provide a means for bringing the CCD bond pads out to
a connector. A goal is to make to the assembly process simple and fool
proof and at the same time build in the required mechanical tolerances
so that the focal plane array can be assembled without adjusting each
CCDs position. Easy replacement of any CCD within the array is also
desirable. We have developed a early concept that achieves these
mechanical goals and have made a 3 x 3 mechanical model in aluminum.

Preliminary concept for CCD module assembly.

> ![](media/image1.png)

Alignment and gluing fixture concept.

![](media/image2.wmf)

Preliminary concept for focal plane array assembly.

![](media/image3.png)

![](media/image4.jpeg){width="3.504166666666667in"
height="3.5006944444444446in"}

### Base plate

The concept for the base plate, which serves as the mechanical mount for
the CCDs and the thermal path to the heat radiator, is developed in
parallel with the CCD mount. It must provide enough strength to
withstand launch loads and enough thermal mass to buffer dynamic heat
loads if we choose to power cycle the on-CCD electronics. A concept for
attaching to the heat radiator will be developed.

### Shield

Black body radiation from other spacecraft components can represent a
major fraction of the thermal load on the focal plane array. Solar
protons will be responsible for the majority of radiation damage to the
CCDs. We are working on a concept of a dual-purpose shield to reduce the
solid angle for black body radiation and to attenuate the sub-100 MeV
proton flux.

## Prototype concepts

During this set of activities we are prototyping our concepts for CCD
packaging and mounting. We are also software modeling concepts for
thermal and particle shielding.

A concept for the CCD mounting system and shield and some initial
prototyping will be complete at the time of the July 2001 ZDR.

### CCD mount

Materials measurements --- radiological, chemical, and mechanical ---
are underway to ensure their compatibility with the silicon of the CCDs.
The optical prescription of the telescope is being used to develop
mechanical placement tolerances for the packaged CCD modules. A series
of 3 x 3 arrays will be prototyped, the first using scrap silicon cut to
the size of a SNAP CCD with expected sawing tolerances. We can verify
that the CCDs are easily assembled with the required tolerance and can
also measure mechanical motion and deformation at 150 K using TV
holography. The second prototype will contain actual SNAP CCDs and can
potentially be readout albeit probably only at room temperature. A third
prototype round is scheduled if needed.

As soon as possible, this CCD mount will become the default packaging
for all testing of SNAP-format CCDs.

### Model radiation flux and shielding

The deployment of material in the thermal and particle shield requires
great care to insure that punch-through debris particles do not amplify
the sub-100 MeV particle flux compared to no shielding at all. Standard
computer transport codes will be run using measured fluences of solar
and galactic particles as input to optimize this shield.

### Perform thermal and mechanical FEA

We will construct a mechanical conceptual model of the focal plane,
shield, mounts, and other attachments. Using standard FEA codes we can
explore the mechanical and thermal performance issues of the imager,
such as

-   Thermal transients from electronic loads.

-   Dissipation of black body load.

-   Cable heat conduction.

-   Support heat leaks.

-   Radiator attachment efficiency.

-   Static mechanical stresses and deflections.

-   Launch vibration/acoustic loads.

-   Kinematic mounting system.

## Build small system concept prototype

The culmination of the imager development is the construction of a 4 x 4
section of the focal plane and an accompanying cryostat. This
demonstration unit will be electronically viable and can be cooled to
operating temperature so that a system performance test can be done when
the readout electronics is available.

## Develop calibration procedures

The important research endeavor of establishing how to calibrate the
imager while in orbit resides in this activity for no logical reason.
One path of research is to determine types of calibration are required
by our use of the instrument, for example

-   Types of flat fields and how to acquire them.

-   Cross wavelength absolute calibration among filters.

-   Standard set of reference stars.

-   On-board radioactive and optical sources.

The other research path is learn what has been done and will be done
with large ground-based and space-based focal plane arrays.

## CD1 planning

A major deliverable at the end of R&D is a cost and schedule for the
construction of the mechanical components of the focal plane array.
Prototype packaging will help establish materials and labor costs. FEA
modeling will produce refined estimates of the mass, mass distribution,
and radiator heat loads that can be used in the design of the
spacecraft.

## Planning for long lead procurements

At this time, no long lead procurements are anticipated.

## R&D deliverables

The table below lists deliverables generated during the R&D effort.

  --------------------------------------------- -------------------------
  **Deliverable**                               **Completion Date**

  CCD mount design                              13-Feb-2002

  Build system prototype                        30-Sep-2002

  Calibration requirements                      2-Oct-2002

  Construction cost and schedule                2-Oct-2002
  --------------------------------------------- -------------------------

## Risk assessment

We cannot identify any high risk issues associated with developing the
CCD packaging.

## Manpower

The table below shows the manpower estimates that have been derived from
a resource load schedule.

+-------------------------+------------------+-----------+-----------+
| **Personnel**           | ##### Category   | #### FTE  |           |
+-------------------------+------------------+-----------+-----------+
|                         |                  | **FY01**  | **FY02**  |
+-------------------------+------------------+-----------+-----------+
| J. Bercovitz            | Engineer         | 1.00      | 1.00      |
+-------------------------+------------------+-----------+-----------+
| Mech. Designer          | Designer         | 0.25      | 0.25      |
+-------------------------+------------------+-----------+-----------+
| N. Hartman              | Engineer         | 0.10      | 0.10      |
+-------------------------+------------------+-----------+-----------+
| Mech. technician        | Technician       | 0.75      | 0.75      |
+-------------------------+------------------+-----------+-----------+
| Scientist               | Scientist        | 1.00      | 1.00      |
+-------------------------+------------------+-----------+-----------+
| M. Metzger              | Scientist        | 0.50      | 0.50      |
+-------------------------+------------------+-----------+-----------+

A brief description of the personnel follows:

-   John Bercovitz is an LBNL engineer with experience in building
    precision experiment components and assembly fixtures.

-   Neil Hartman is an LBNL engineer whose expertise is finite element
    analysis.

-   The mechanical designer will either come from the pool at LBNL or
    one of the collaborating institutions. Candidates have been
    identified.

-   The mechanical technician will either come from the pool at LBNL or
    one of the collaborating institutions.

-   Mark Metzger is

-   The scientist is a graduate student or post doc. No one has been
    identified yet.

## Budget summary 

The table below contains the budget summary in k\$ excluding scientist
salaries.

  ---------- ---------- ---------- ---------- ---------- ---------- ----------
  **WBS**               **FY01**                         **FY02**   

             EDIA       Material   Total      EDIA       Material   Total

  A.1.12.2   349        82         430        365        58         423
  ---------- ---------- ---------- ---------- ---------- ---------- ----------

## Schedule summary

A schedule summary is shown below which tracks the narrative above. The
fully expanded schedule is provided elsewhere.

![](media/image5.wmf){width="5.996527777777778in"
height="3.9298611111111112in"}