An Agile Multi-Use Nano Star Camera for Constellation Applications

Transcription

1 An Agile Multi-Use Nano Star Camera for Constellation Applications Scott Palo 1,2, George Stafford 2 and Alan Hoskins 1 1 University of Colorado 2 Blue Canyon Technologies

2 Partnership The BCT technical staff has over 100 years of combined experience working on DOD, NASA and commercial space projects including Worldview and the Hubble Space Telescope among others. AES has a long history of technical excellence in Astrodynamics, GNSS, Small Satellites and Remote Sensing. 7 AES students have been finalists in the Frank J. Redd Student Scholarship competition since Extensive experience building, testing and operating scientific instruments for NASA. Proving NASA qualified technicians and facilities. LASP instruments have been sent to all planets in the solar system, including Pluto.

3 Introduction Recent NSF missions (RAX-2, DICE, CSSWE) have shown the ability to conduct cutting edge science from a cubesat. Precision attitude (sub-arc minute) is required for the next generation earth and space science missions Earth Observing Missions: One arc-minute is a 175m error from 600km With scenes on the order of 10kmx10km (2048x2048 imager with 0.5m pixel resolution) 20 arc-minute knowledge is required to provide scene overlap Space Weather Mission: Measuring in-situ winds Instrument measures the free-stream velocity V measured = V sc + V wind, where V sc is about 8000m/s Pointing must be better than 18 arc-seconds to achieve a 4 m/s wind error Attitude knowledge of arc-minutes is needed to support such science missions

4 Introduction Recent NSF missions (RAX-2, DICE, CSSWE) have shown the ability to conduct cutting edge science from a cubesat. Precision attitude (sub-arc minute) is required for the next generation earth and space science missions A star Earth camera Observing Missions: is required to achieve this One arc-minute is a 175m error from 600km level of attitude knowledge With scenes on the order of 10kmx10km (2048x2048 imager with 0.5m pixel resolution) 20 arc-minute knowledge is required to provide scene overlap Space Weather Mission: Measuring in-situ winds Instrument measures the free-stream velocity V measured = V sc + V wind, where V sc is about 8000m/s Pointing must be better than 18 arc-seconds to achieve a 4 m/s wind error Attitude knowledge of arc-minutes is needed to support such science missions

5 Star Camera Basics Hardware Baffle Lens Detector Software Background compensation Centroiding Star Catalog Star Identification Attitude Solution

6 Star Camera Basics Hardware Challenges Off axis light rejection Lens performance and robustness Baffle Lens Detector Star Catalog Background compensation Detector performance On orbit calibration Centroiding Star catalog organization Efficient catalog searching Star Identification Attitude Solution Software

7 BCT Nano-Star Camera (NSC-1) Specification Attitude solution update rate Cross-axis Accuracy NSC-1 Performance 5 Hz 7 arc-sec (1s) Accuracy about roll axis 24 arc-sec (1s) Time-to-first-fix 2 seconds Field of View 11.6 o x 9 o Mass 0.5 kg 1 Volume 5 x 5 x 10 cm 1 Nominal Power Consumption Operating Voltage Data Interface (optional control electronics) 1 including baffle 0.5W 5 +/-.1 Vdc RS-422, I2C or SPI

8 BCT Nano-Star Camera (NSC-1) Specification Attitude solution update rate Cross-axis Accuracy NSC-1 Performance 5 Hz 7 arc-sec (1s) Accuracy about roll axis 24 arc-sec (1s) Time-to-first-fix 2 seconds Field of View 11.6 o x 9 o Mass 0.5 kg 1 Volume 5 x 5 x 10 cm 1 Nominal Power Consumption Operating Voltage Data Interface (optional control electronics) 1 including baffle 0.5W 5 +/-.1 Vdc RS-422, I2C or SPI

9 BCT Nano-Star Camera (NSC-1) Specification Attitude solution update rate Cross-axis Accuracy NSC-1 Performance 5 Hz 7 arc-sec (1s) Accuracy about roll axis 24 arc-sec (1s) Time-to-first-fix 2 seconds Field of View 11.6 o x 9 o Mass 0.5 kg 1 Volume 5 x 5 x 10 cm 1 Nominal Power Consumption Operating Voltage Data Interface (optional control electronics) 1 including baffle 0.5W 5 +/-.1 Vdc RS-422, I2C or SPI

10 100 NSC-1 Images Camera Mode Short exposure daylight image of Mariner Medium exposure night image of Dan s car Camera Mode Features Linear and exponential scaling Variable exposure time Variable analog gain

11 NSC-1 Lens Characteristics Designed specifically with CubeSat or other microsat applications in mind. The lens assembly consists of a minimum number of elements that support rapid, high-volume assembly. Lens is robust enough in design that it requires no active alignment during assembly and instead relies on simple mechanical tolerances. The lens is athermal from -30 to +60 C and has been thermal cycled and tested in the LASP Tvac.

12 NSC-1 Baffles CU LASP designed Key to NSC-1 performance Challenging in small volume NSC-1 baffle ~1 x 2.6 x 2 and fully integrated into the unit

13 Baffle Performance Simulated with Zemax -30dB within 2 o of the star camera field of view -77dB at dB normal to boresight

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15 Baffle Extinction vs. FOV in db BCT XACT Ruby 0-20 Horizontal Slice Vertical Slice Average Radial Slice Baffle Extinction (db) Earth KO Sun KO -120 Extinction = Sun Keep Out Zone Extinction Earth Keep Out Zone Angle from Boresight ( )

16 Heliostat testing at LASP NSC-1

17 Initial System Testing Loveland Pass 11,990 Precision motorized telescope mount (3 arcsec) NSC-1 ready for testing

18 NSC-1 Star Field Images More than 50 stars identified in NSC o x9 o field of view Saturated stars, dim stars and closely spaced stars are eliminated for processing

19 NSC-1 Star Field Movie Orbit Rate Scintillation due to poor atmospheric conditions during testing *High Winds *High aerosol content due to forest fires

20 NSC-1 Star Field Movie 1 degree/sec

21 NSC-1 Image Sensitivity Magnitude 6.5 star Detected on multiple pixels improves centroiding Intensity signal to noise ratio > 200 (23dB) Magnitude 7 star faintest naked-eye stars visible from "dark" rural areas located some 140 miles (200 km) from major cities and some 30 miles (50 km) from the nearest town of population 5000 International Comet Quarterly

22 Video of magnitude 6.4 and 7.5 magnitude star as seen from NSC-1 Magnitude 6.4 star Magnitude 7.5 star

23 NSC-1 Pointing Solution Performance: 10 First Light X 10 Y 20 Z NSC-1 stationary 1 Hz solution Mean motion removed RMS result s x = 2.0 s y = 2.4 s z = 7.4

24 attitude attitude Nominal Attitude Mode Timing (5Hz) 200ms 200ms 200ms a a a time

25 attitude attitude attitude SSA and Proximity Operations Approach 200ms 200ms 200ms Camera Mode a a a b b b b time

26 SSA and Proximity Operations Example Linear Scaling with Cubesat at 15m

27 SSA and Proximity Operations Example Linear Scaling with Cubesat at 5m

28 Region of Interest (ROI) Mode Linear Scaling with Cubesat at 2m ROI overlay Star Field

29 Region of Interest (ROI) Mode Exponential Scaling with Cubesat at 2m User specified ROI overlay Star Field

30 NSC-1 as part of a complete ADCS XACT Capability Specification Performance Spacecraft Pointing Accuracy ± deg (1-sigma) for 2 axes ± deg (1-sigma) for 3 rd axis Spacecraft Lifetime XACT Mass XACT Volume XACT Nominal Power Consumption XACT Peak Power Consumption 1 Year.7 kg 10 x 10 x 5 cm (0.5U) 0.5W 2.0W XACT Operating Voltage 12±2V Data Interface RS-422 (can support I2C and SPI) NSC-1 Slew Rate (8kg, 3U CubeSat) 10 deg/sec Micro reaction wheel

31 XB1: A complete CubeSat bus GN&C Star Tracker C&DH EPS Star Tracker XB1

32 Current Activities Product Company/Organization Status Launch/ Delivery Date XACT CU/LASP NASA Sounding Rocket Under Contract Launch Oct 2013 (Components) XACT University of Colorado - HiLITE Under Contract Delivery 4Q13 XACT NASA JPL ISARA In Discussions Launch 2015 XACT AFRL Under Contract Delivery 3Q14 XACT CU/LASP MinXSS In Proposal TBD NSC-1 JPL INSPIRE Under Contract Launch Aug 2014 NSC-1 NASA Marshall CubeSat Development Project Under Contract Delivered July 2013

33 CU LASP/AES MinXSS Goal to better understand the solar irradiance energy distribution of solar flare soft X-ray (SXR) emission and its impact on Earth s ionosphere, thermosphere, and mesosphere (ITM) Use a commercial x-ray spectrometer (x123) to observe the soft x-ray solar spectrum from <1 kev (>12 Å) to >5 kev (<2.5 Å) Resolution: < 0.5 kev Accuracy: < 30% Measures in a gap of current knowledge XACT ADCS

34 Summary The dynamic capability and numerous operational modes allow NSC-1 to be used for attitude knowledge and space situational awareness. BCT NSC-1 is a exceptionally capable star camera in a CubeSat compatible form factor which will enable the next generation of CubeSat constellation missions.