# Presentation: 485315

## Slide 1

## ISAL Team

- Mike Amato		System Engineering
- Jeff Bolognese		Structural Analysis
- Art Bradley		Star Field /Fine Guidance
- Jennifer Bracken		ISAL Team Lead
- Judy Brannen		Mechanical Design
- Mick Correia		Mechanical Design
- Paul Earle		Electrical
- Dennis Evans		Optics
- Rodger Farley		Mechanical Systems
- Landis Markley		Guidance, Navigation, and Control
- Wes Ousley		Thermal
- Mike Roberto		ISAL Systems
- Carl Stahl		Detectors
- John Wood		ISAL Science Liaison
- Eric Young		Electro-optical Systems

## Summary

- Requirements
- Trades and Issues
- Instrument Diagram
- Orbit Parameters
- Observation Strategy Summary
- Optics
- Detectors
- Mass, Data Rate
- Conclusions

## Requirements

## Trades and Issues

- Baselining Hubble type structure rather than lower structure
- Hubble like and upper structure tripod. Metering structure
- is stiffer, less obscuration, and more thermally isolated. However,
- it has higher mass and more complicated baffle integration.
- 2. Converged on ‘two vane’ shutter design. Advantage is the
- same illumination time for each pixel, but feedback control
- is needed. Alternate shutter type did not need feedback control
- but required very rapid operation to minimize time differences
- in pixel illumination.
- 3. Baselining five degrees of freedom secondary mirror adjustment
- Based on flight design, because secondary mirror is the most sensitive
- to alignment errors. Tertiary mirror adjustment mechanism does not
- seem to be needed.
- 4. May not need thermal control of metering structure, but this could easily
- be added (approximately 150 W). Plan to use low coefficient of thermal
- expansion graphite epoxy materials.

## Trades and Issues (continued)

- 5. Do not see unusual stray light problems, but careful baffling is necessary.
- 6. Baselining 16 bit analog to digital converters. Could also use 12 bit A/D converters with multiple gains.
- 7. Baselining fixed filters on focal plane which requires stepping across focal plane. Advantage is the reduction in the number of mechanisms (filter wheel
- not needed.
- 8. Future Trade – consider placements of spectrographs so behind focal plane to
- reduce stray light.

## Instrument Diagram

## Orbit Parameters

- Modified Chandra orbit for complete observation of
- ~ northern or southern ecliptic in one orbit and equalizing
- spectrograph and focal plane observation times.
- Radius of perigee			3.0 Earth radii
- Radius of apogee			24.5 Earth radii
- Period				3.0 days
- Height for data collection		=/> 60 x 10^3 km
- Time spent near perigee		12 hours
- Time for focal plane observations	29 hours
- Time using spectrograph		31 hours

## Observation Strategy Summary

-    Art Bradley and Landis Markley provided the inputs.
- Inside electron belts, slew 180 degrees, download data, orbit maintenance,
- shutter closed
- Outside electron belts, use ACS guide star CCDs on focal plane for fine
- pointing control when shutter is open
- Observation time = 200 seconds
- Focal plane shutter is then closed for 20 seconds while focal plane is read out,
- drift is fixed, and pointing is changed by 1⁄4 of CCD position
- 5.   Sky observations on focal plane are repeated for 480 steps in one direction,
- covering about 5 degrees in 29 hours

## Optics

## Detectors

## Mass

## Data Rate

- Focal plane average data rate during an observation	40 M bits/sec
- (144 CCD arrays with 1600x1600 pixels, 44 HgCdTe arrays with 2000x2000 pixels,16 bits per pixel, 220 seconds to complete observation plus read out focal plane)
- Average data rate during spectrograph observation	73 K bits/sec
- (one HgCdTe array with 1000 x 1000 pixels, 16 bits per pixel)
- Data collected per orbit (assuming about half focal plane observations and half spectrograph observations, assume data compression by factor of 2)
- 		Focal plane telemetry per orbit		2.1 T bits
- 		Spectrograph telemetry per orbit		4.0 G bits
- 		Housekeeping telemetry per orbit		47 M bits
- 4. If focal plane data taken all the time, and data compressed by factor or two,
- total data collected during orbit about 4.2 T bits.

## Backup Slides

## Orbit Parameters

## Data Rate