An Agile Multi-Use Nano Star Camera for Constellation Applications

Scott Palo1,2, George Stafford2 and Alan Hoskins1

1 University of Colorado 2 Blue Canyon Technologies 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 2003.

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. 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

• Vmeasured = Vsc + Vwind, where Vsc is about 8000m/s • Pointing must be better than 18 arc-seconds to achieve a 4 m/s wind error

Attitude knowledge of 15-20 arc-minutes is needed to support such science missions 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: A star• Onecamera arc-minute is a 175mis requirederror from 600km to achieve this • With scenes on the order of 10kmx10km (2048x2048 imager with 0.5m pixel resolution)level 20 of arc-minute attitude knowledge is required knowledge to provide scene overlap – Space Weather Mission: Measuring in-situ winds • Instrument measures the free-stream velocity

• Vmeasured = Vsc + Vwind, where Vsc is about 8000m/s • Pointing must be better than 18 arc-seconds to achieve a 4 m/s wind error

Attitude knowledge of 15-20 arc-minutes is needed to support such science missions Star Camera Basics Hardware

Baffle Lens Detector Software

Background compensation

Centroiding

Star Attitude Star Catalog Identification Solution Star Camera Basics Hardware

BaffleChallengesLens Detector Software • Off axis light rejection • Lens performanceBackground and robustness compensation • Detector performance • On orbit calibration Centroiding • Star catalog organization • Efficient catalog searching Star Attitude Star Catalog Identification Solution BCT Nano-Star Camera (NSC-1)

Specification NSC-1 Performance Attitude solution update rate 5 Hz 7 arc-sec (1s) Cross-axis Accuracy

Accuracy about roll axis 24 arc-sec (1s) Time-to-first-fix 2 seconds Field of View 11.6o x 9o Mass ≤ 0.5 kg1 Volume ≤ 5 x 5 x 10 cm1 Nominal Power ≤ 0.5W Consumption Operating Voltage 5 +/- .1 Vdc Data Interface (optional RS-422, I2C or SPI control electronics) 1 – including baffle BCT Nano-Star Camera (NSC-1)

Specification NSC-1 Performance Attitude solution update rate 5 Hz 7 arc-sec (1s) Cross-axis Accuracy

100

200

300

400 100 Medium exposure night image of Dan’s car

500

200 600

300 700

400 800

900 500

1000 600 200 400 600 800 1000 1200 Camera Mode Features 700 Linear and exponential scaling 800 Variable exposure time 900

Variable analog gain 1000 200 400 600 800 1000 1200 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. 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 Baffle Performance • Simulated with Zemax • -30dB within 2o of the star camera field of view • -77dB at 27° • -108dB normal to boresight

Baffle Extinction vs. FOV in dB BCT XACT Ruby

0 Horizontal Slice Vertical Slice -20 Average Radial Slice

-40

-60 Earth KO -80

Baffle Extinction (dB) Sun KO -100

-120 Extinction = 10-10.0 @ Sun Keep Out Zone Extinction  10-7.7 @ Earth Keep Out Zone -140 -80 -60 -40 -20 0 20 40 60 80 Angle from Boresight () Heliostat testing at LASP

NSC-1 Initial System Testing

• Loveland Pass 11,990’ • Precision motorized telescope mount (3 arcsec)

NSC-1 ready for testing NSC-1 Star Field Images

More than 50 stars identified in NSC-1 11.6ox9o field of view Saturated stars, dim stars and closely spaced stars are eliminated for processing NSC-1 Star Field Movie – Orbit Rate

Scintillation due to poor atmospheric conditions during testing

*High Winds *High aerosol content due to forest fires NSC-1 Star Field Movie – 1 degree/sec 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 Video of magnitude 6.4 and 7.5 magnitude star as seen from NSC-1

Magnitude 6.4 star Magnitude 7.5 star NSC-1 Pointing Solution Performance: First Light 10’’ • NSC-1 stationary X • 1 Hz solution

10’’ • Mean motion removed Y • RMS result s = 2.0” 20’’ x sy = 2.4” Z sz = 7.4” Nominal Attitude Mode Timing (5Hz)

200ms 200ms 200ms

attitude attitude

a a a time SSA and Proximity Operations Approach 200ms 200ms 200ms

Camera Mode

attitude

attitude attitude

a b a b b a b time SSA and Proximity Operations Example

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

Linear Scaling with Cubesat at 5m Region of Interest (ROI) Mode

Linear Scaling with Cubesat at 2m

ROI overlay

Star Field Region of Interest (ROI) Mode

Exponential Scaling with Cubesat at 2m

User specified ROI overlay

Star Field NSC-1 as part of a complete ADCS XACT Capability Specification Performance Spacecraft Pointing Accuracy ± 0.003 deg (1-sigma) for 2 axes ± 0.007 deg (1-sigma) for 3rd axis

Spacecraft Lifetime ≥1 Year XACT Mass ≤.7 kg XACT Volume ≤10 x 10 x 5 cm (0.5U) NSC-1 XACT Nominal Power ≤0.5W Consumption XACT Peak Power Consumption ≤2.0W XACT Operating Voltage 12±2V Data Interface RS-422 (can support I2C and SPI) Slew Rate (8kg, 3U CubeSat) ≥10 deg/sec Micro reaction wheel XB1: A complete CubeSat bus

GN&C Star Tracker

XB1 C&DH EPS Star Tracker 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 Under Contract Delivered July 2013 Development Project CU LASP/AES MinXSS XACT ADCS 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 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.