AIAA/USU Small Satellite Conference 2007 Paper No. SSC07-VIII-2

Transcription

1 Digital Imaging Space Camera (DISC) Design & Testing Mitch Whiteley Andrew Shumway, Presenter Quinn Young Robert Burt Jim Peterson Jed Hancock James Peterson AIAA/USU Small Satellite Conference 2007 Paper No. SSC07-VIII-2

2 Introduction Need Was Identified Low cost radiation-hardened space-rated camera Enabling technology for small satellite community Developed Requirements Low Cost Radiation hardened Lightweight High reliability Adaptable optics Simple interface

3 Electrical Design Heritage Generation 1 Sun sensor/pointing mirror control Generation 2 Digital Image Space Camera (DISC) Breadboard Generation 3 Digital Image Space Camera (DISC) Baseline Design NASA AIM Mission Launched March 25, 2007 Radiation hardened design Sub-arcsec knowledge DISC breadboard Flight and commercial parts Functional electrical, software, and optical testing DISC baseline design Full characterization testing Reached TRL 5 in 2007

4 DISC Baseline Design Visible focal plane array 1 megapixel Mass ~0.6 kg Power < 2 W Radiation Hardened >100 krad (Si) Baseline optics customizable to mission-specific needs Field of view, aperture size, and focus distance Signal-to-noise, Integration time, image quality Temperature range -30ºC to +70ºC (tested range)

5 DISC Body Aluminum housing Dimensions 87 x 70 x 230 mm 3.5 x 2.75 x 9 inches Barrel contains customizable optics N 2 purge port Contamination control Purge port 70 mm Micro-D Connector 230 mm Barrel with Customizable Optics Focal Plane Array 87 mm FPGA 0.1 thick walls 165 mm

6 DISC Focal Plane Array STAR 1000 Focal Plane Array 1 megapixel array Operates in visible spectrum 400 to 1000 nm Manufactured by Cypress/Fillfactory Radiation hardened >230 krad (Si) Selected because of radiation tolerance CMOS technology Features On-board 10-bit ADC Simplifies electronics design Windowing and pixel binning

7 DISC Electronics Focal Plane Array Electronics Hardware Radiation tolerant parts >100 krad(si) Field Programmable Gate Array Controls the electronics Greater mission flexibility Architecture/Performance LVDS I/O (TIA/EIA-644 compatible) Modeled after Camera Link standard 18 control/status registers 4 discrete digital control inputs Enables video mode, snapshot mode, reset the FRT Frame rates* FPGA Frame Size 1024 X X X X Frames per Second (fps) *Using 1ms integration time

8 DISC Optics Baseline Optical Design 4 Lenses Fold mirror Spectral filter (500 to 700 nm) Reduces chromatic aberrations Focal Plane Optical Performance 15 μm pixel pitch Fill factor of 44% Modulation Transfer Function 0.37 in Y axis 0.26 in X axis Quantum Efficiency X Fill factor of ~22% Within spectral region used Tilted Filter Radiation Tolerant Glass Lenses FPA Window Fold Mirror

9 DISC Testing Program Tests conducted to characterize performance Optical Imaging Distortion Straylight Radiometric Responsivity Dynamic range Dark Current & Noise Uniformity Linearity System Noise Electrical/Software Functional testing Environmental Thermal-Vacuum Vibration (board only) EMI

10 Imaging Test Viewed bar pattern target View at range of distances (pass through best focus) Generate Contrast Transfer Function (CTF) Find Modulation Transfer Function (MTF) by scaling data Compared results with modeled predictions

11 MTF Comparison CTF with Target Distance Comparison of Derived MTF Results agree reasonably well with prediction

12 Distortion Measurement Project autocollimation source into DISC Map source position with pixel position Result Optical distortion <0.7% over field Matched our modeled predictions very closely

13 Straylight Measurements Measured out-of-field glints and tested for ghosting Sun illumination on DISC baffles Measured off-axis response Angles 20º to 50º from normal Results Quantified one glint No ghosts found Generated straylight rejection curve In-field source DISC on rotary stage for sun illumination Glint Vert Scan Horiz Scan

14 Radiometric Measurements Radiance responsivity Viewed calibrated integrating sphere Irradiance responsivity Derived from radiance responsivity Direct measurement using collimator and calibrated source Photo-voltaic response curve Linearity +/-5% over most of range Dark current ~7 counts/sec at 20ºC RMS noise ~0.1% of dynamic range Point Response Function

15 Thermal Analysis/Testing Performed thermal analysis Operated DISC in TVAC chamber -30ºC to +70ºC 8 thermal cycles Characterized with temperature Radiometric Electrical Performed well and matched predictions

16 Structural Analysis/Testing Performed at board-level Further work will test DISC at system level Random vibration testing successful 1st mode deflection of (3σ) (FPA location)

17 EMI Testing Has undergone full suite of EMI/EMC tests Passed per MIL-STD-461C Setup in anechoic chamber Using near-field probe

18 Summary Designed and developed miniature radiation hardened imager Designed for: Interplanetary missions Rendezvous/proximity operations Space Situational Awareness Conducted host of tests to characterize imager Performing well Delivering first flight unit Aug 2007 Currently working on next generation system 28 volt system Next generation focal plane