ISUAL System Design H. Heetderks. PDR 31 August 2000NCKU UCB Tohoku ISUAL System Design H....

ISUAL System Design

H. Heetderks

PDR 31 August 2000NCKU UCB Tohoku ISUAL System Design H. Heetderks

2

ISUAL Operations Overview


3

ISUAL Science Operations Strategy

• Instrument Mounted on ROCSAT2 S/C in 891 Km Polar Orbit

• Science Data Collected on Night Side of Orbit

• ROCSAT2 S/C reoriented to Point ISUAL at Limb or Somewhat Below at Beginning of Pass

• Pointing may be Either Along the Track or Cross Track

• Data are Stored and Compressed in on Board Memory and Transferred to the S/C Memory at the end of each Orbit

• After 14 Orbits, the Data are Telemetered from the S/C Memory to the Ground


4

ISUAL Instrument Complement

• Sprite Imager– Gated Intensified CCD camera– 512 X 128 (was 80) pixel resolution– 20 deg. X 5.0 (was 3.15) deg. Field of View– Filter wheel has six selectable filters

• Spectrophotometer– Six photometer modules are identical except for spectral characteristics– 20 deg. X 5.0 (was 3.15) deg. Field of View– All photometers are boresighted in the same direction as the imager– All six channels are sampled at a 10 kHz rate


5

ISUAL Instrument Complement (con’t)

• Array Photometer– Two photometer units, identical except for optical filter bandpass– 20 deg. X 3.15 deg. FOV divided into 16 channels– Selectable sample rate– Boresight same as other instruments

• Associated Electronics Package– Performs power distribution and control– Performs command decoding– Controls instrument and sensors– Performs compression of images– Stores 128 Mbytes in Mass Memory– Generates CCSDS telemetry packets


6

Sprite Imager Mechanical Properties

• Volume: ~250 (was 240) H x 240 W x 362 L (mm)

• Mass: 7.1 (was 6.6) kg

• Max Power: 14.0 W


7

Spectrophotometer Mechanical Properties

• Volume: ~187 (was 231) H x 156 (was 141) W

• x 244 (was 237) L (mm)

• Mass: 5.7 (was 5.4) kg



8

Array Photometer Mechanical Properties

• Volume: ~290 H x 244 W x 395 (was 410) L (mm)

• Mass: 11.0 kg



9

AEP Mechanical Properties

• Mass: 5.2 (was 5.1) kg



10

ISUAL System Electrical Block Diagram


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ISUAL Operational Modes

• Sprite Continuous Mode– Imager is continuously taking images at a 100 frame/sec rate– Array Photometer is continuously sampled at a 20 or 2 kHz rate– Spectrophotometer is continuously sampled at a 10 kHz rate– All data are written into a series of circular memory buffers– Upon meeting trigger criteria on Spectrophotometer data, a selected block of

data are saved in Mass Memory for compression and transfer to T/M– Selectable trigger parameters include channel, level, rise time, and pre-trigger

block size and post-trigger block size

• Sprite Burst Mode– Same as continuous mode except sample rate is 650 Hz for a limited period– Price of high sample rate is ~80% dead time

• Auroral Mode– All instruments operate at a constant rate of 1 sample/second– All data saved, compressed, and transferred to S/C for downlink


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ISUAL Science Data Handling Strategy

• AEP Collects Digital Data from each Instrument During each Nightside Pass

• Raw Data Stored in 128 Mbyte Memory

• Raw Data in Memory are Compressed by Dedicated DSP System

• Data Compression will Continue for a Portion of the Dayside Pass following Completion of Data Collection

• Compressed Data are Transferred to S/C Memory in 67,108,864 Bit Blocks of PVCF’s Packed with CCSDS Source Packets

• S/C Memory Stores up to 256 Kbytes of Compressed ISUAL Data

• Separate Channel for Real Time & Housekeeping Data

• S/C Memory Downlinked to Taiwan Twice per Day

• Ground Data System Discussed Later


13

Resource Requirements Summary -- Mass

Component Held byAstrium (Kg)

Allocatedto ISUAL

20 April, 2000MassSummary

18 May, 2000MassSummary

Sprite Imager 10.0 8.0 6.56 7.60

Spectrophotometer 9.0 5.0 5.37 5.37

Array Photometer 13.0 12.0 11.0 11.0

AssociatedElectronicsPackage

6.5 5.0 4.99 4.99

Totals 38.5 30.0 27.91 28.95

22 Aug, 00MassSummary

7.6

5.7

11.0

5.22

29.5


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Resource Requirements Summary -- Power

Mode 1 Heaters Only 16.0 W

Mode 2 DPU Only 3.9 W

Mode 3 DPU with Memory Save 6.6 W

Mode 4 Full Science in Idle 30.8 W

Mode 5 Data Compression 36.0 W

Mode 6 Full Data Taking with Compression 48.0 W

Typical Orbit: Mode 6 -- 40% Mode 5 -- 30% Mode 4 -- 30% * Gives 40.0 Watts Orbit Average (40.0 W Allocated)

*Gives 48.0 Watts Peak (100.0 W Allocated)

Note that the above assumes no heater power needed during science operationsThis is subject to change as a result of ongoing thermal analysis.


15

Resource Requirements Summary (Con’t)

• T/M Downlink: 1 Gbit per day

• Command Link: 50 Kbits per day Occasional 32K byte S/W upload

• Attitude Control: 0.5 deg Pointing . 1.0 Arc-min Knowledge

• Thermal Control: (Temp of Deck and Surroundings)

• Contamination: TBD

Operating Non-operatingInstruments -20C. to +30C. -35C. to +50 C.AEP -40C. to +50C. -55C. to +55 C.


16

Alignment Strategy

• Optic Cube on each Instrument Provided by Instrumenter at measured offset to Instrument Optical Axis

• Instruments are Mounted on the Spacecraft Deck and Angles Measured to Star Tracker by S/C Contractor to 0.5 Arc-min


17

Thermal Control Strategy

• Original UCB Design was based on the Thermal Environment defined in the ISUAL Specification Document

– Assumed heat was dumped to deck plate and deck plate temperature controlled by the spacecraft

• Revised strategy accommodates insulating deck plate with individual radiators on each box

– Instrument Designs modified to bring heat to top surface

– Interface Plate made sufficiently thick to be considered isothermal

– NSPO thermal design team provides radiator which keeps Interface Plate within prescribed temperature range

– Make-up heaters used to manage low temperature case

– UCB verifies boxes operate within specification over allowed temperature range Interface Plate

– UCB testing can be done in existing facilities


18

Contamination Control Plan

• Electronics and Mechanisms Assembled and Tested in Class 100,000 Clean Areas

• Optical Parts Assembled on Class 100 Clean Bench

• Electronics and Mechanisms Cleaned Prior to Assembly with Optics

• Instruments Operated and Tested in Class 100,000 Clean Areas

• Instruments cleaned prior to delivery

• Instruments Shipped in Double Bags


19

Spacecraft to ISUAL Electrical Interface

• ISUAL Receives 28 Volt Nominal Power on a Pair of Redundant Switched 6 Amp Services

• Each Service Powers one of a Pair of Redundant LVPS Systems– Switching is automatic; no need for S/C controlled relay

• Science Data are Transferred to S/C via a High Rate 4 Line Serial-with-Handshake 422 Interface

– Data transferred in blocks of 67,108,864 bits under software handshake– Within each block, data are packed into 1,108 byte PVCF’s (3 header bytes gen by ISUAL)– Within each PVCF, data are wrapped in CCSDS Source Packets

• Two App ID’s for each Science Data Product– One type for Header– One type for Science Data

• Maximum Packet length is 4,096 bytes including header and trailer• Some products take up to 100 packets to transmit


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Spacecraft to ISUAL Electrical Interface (con’t)

• Realtime and Engineering Data as well as ISUAL Communications to S/C is via a Dedicated low rate single line serial 422 interface

– Format of CCSDS Packets is same as for Science Interface except maximum packet length is 256 bytes– Same CCSDS format used for ISUAL communications with the S/C, e.g. request to send Science Data

• Commands from S/C to ISUAL via a low rate serial single line 422 int’f– All ISUAL command decoding done in ISUAL– S/C provides real time commands only

• A single additional power service from the S/C operates thermostatically controlled make-up heaters in each of the ISUAL boxes

– Heaters and thermostats built into boxes by UCB

• S/C Senses 1 Thermistor in each of the four ISUAL Boxes– Controlled by OBMU

ISUAL System Design H. Heetderks. PDR 31 August 2000NCKU UCB Tohoku ISUAL System Design H....

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