On-Orbit Performance of the BCT XB-1 Spacecraft and GN&C Components

On-Orbit Performance of the BCT

XB-1 Spacecraft and GN&C

Components

Devon Sanders, Matt Baumgart, Dan Hegel, Bryan Rogler

August 5, 2017

About BCT

industry veterans previously from Ball Aerospace and the Laboratory for Atmospheric and Space Physics (LASP)

• Advancing the state of the art in small satellites:

– Smallsat components & systems (Nano Star Trackers, Reaction Wheels, Power Systems) – Precision pointing Spacecraft Buses

– Complete small spacecraft turnkey systems

• BCT Staff have developed, tested and flown systems on more than 30 space missions • Staff & Facility:

– Staff of over 50 and growing (engineering, production, procurement, support)

– 23,000 square feet for manufacturing, test, and mission operations center

– Recent equipment & systems automation investments

– IR&D: Design enhancements for volume manufacturing & test

In 2016, Inc. Magazine listed BCT as the

Number 1 Fastest Growing Private Engineering Company in the United States, and #162

XB Spacecraft

• Spacecraft Bus

– Guidance Navigation & Control (GN&C) 3-axis control & stellar navigation

– Electrical Power Subsystem (EPS) battery, solar arrays, charge control, & power distribution and telemetry

– Command and Data Handling (C&DH)

onboard data formatting, command, control, and telemetry for the various subsystems, and payload interfaces

– RF communications (RF Comm) multiple options (x-Band, S-Band, UHF, or GlobalStar) – Payload Accommodation serial interfaces

over various formats including I2C, SPI, or LVDS as well as discrete digital telemetry inputs and analog data inputs

• Integration & Test

• Launch Vehicle Integration

• Mission Operations

RAVAN Background

• RAVAN XB-3 (3U CubeSat) launched

on November 11, 2016 on Atlas V

– Earth radiation mission led by Johns

Hopkins University Applied Physics

Laboratory (APL)

– Funded through NASA ESTO’s InVEST

program

– Sun synchronous orbit, ~580 km

• First flight of BCT XB spacecraft

• Operated out of BCT facility in

Boulder, CO

• Originally 6 month mission, extended

until April 2018

100 120 140 160 180 200 220 240 260 280 0 0.1 0.2 0.3 0.4 0.5 0.6 A n g le E rr o r (d e g ) Time (min) Sun Point Angle Error

100 120 140 160 180 200 220 240 260 280 0 2 4 6 8 10 12 A n g le E rr o r (d e g ) Time (min) Sun Point Angle Error

RAVAN Safe Mode Performance

• Autonomously maintains spacecraft safety in safe

mode using coarse sun sensors with reaction wheels

• Successfully demonstrated

after RAVAN deployment

• Control error is less than 0.6°

– 2 orbits of data shown with

eclipse times excluded

– Misalignment of sun sensor

to panel normal is not

included

ECLIPSE

ECLIPSE ECLIPSE

0 2 4 6 8 10 12 14 16 18 20 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 0.15 0.2 0.25 A n g le E rr o r (d e g ) Time (hr) Fine Ref Angle Error

X Y Z

RAVAN Fine Pointing Performance

(normal mission operations)

• Pointing performance (1σ) excluding wheel zero-speed crossings (< 50 RPM)

– X axis: 14 asec mostly about tracker boresight – Y axis: 6 asec across tracker boresight

– Z axis: 7 asec mostly across tracker boresight

• Results comparable to those obtained for MinXSS

– MinXSS results match independent payload instrumentation – RAVAN payload not capable of similar measurements

• Pointing errors analyzed for 18 hours (12 orbits) of data

– Attitude control with single tracker in the loop

– Can operate both trackers in the loop for cross-boresight performance in all axes

– No effort made to optimize wheel speeds or suspend torque rod operations

• Angle error includes occasional zero-speed wheel crossings that induce transient errors above baseline

– 4 crossings/orbit

– Mitigations available for missions that require them

0 5 10 15 20 25 30 35 40 45 50 10 20 30 40 50 60 70 80 90 100

Attitude Error (arcsec)

C u m u la ti v e P e rc e n ta g e ( % )

Fine Ref - Cumulative Pointing Error (RPM > 50)

X Y Z

Zero-Speed Crossings 1σ

600 700 800 900 1000 1100 1200 -2500 -2000 -1500 -1000 -500 0 500 1000 1500 2000 2500 W h e e l S p e e d ( rp m ) Time (min) Reaction Wheel Speed

X Y Z

RAVAN Momentum Control

• Successfully demonstrated momentum control to a desired momentum

– Torque rods used for momentum control – Momentum bias is configurable

• Figure shows transition between safe mode to fine reference pointing

– Desired momentum in Fine Reference Point Mode is 1 mNms in all three axes and 0 mNms in Sun Point Mode

– Enters Fine Reference Point Mode just before 800 seconds

– Data decimated down to 50 seconds (and data between 800 and 950 seconds was not downlinked)

600 700 800 900 1000 1100 1200 -0.5 0 0.5 1 1.5 2 M o m e n tu m ( m N m s ) Time (min) Spacecaft Inertial Momentum

X Y Z SUN POINT FINE REF NO DATA Commanded Momentum Bias NO DATA

XB-3 Systems Performance

• Electrical Power Subsystem

– Healthy bus and battery voltages

– Battery charge and discharge current is nominal

8 0 2 4 6 8 10 12 14 16 18 11 12 13 14 15 16 17 18 19 20 V o lt a g e s ( V o lt s ) Time (hr) Spacecraft Voltages Battery Bus 0 2 4 6 8 10 12 14 16 18 -2 -1.5 -1 -0.5 0 0.5 1 1.5 C u rr e n t (A m p s ) Time (hr) Battery Current

0 2 4 6 8 10 12 14 16 18 0 50 100 150 200 250 300 C o m m a n C o u n t Time (hr)

FSW Command Accept Count

XB-3 Systems Performance

• Thermal

– Bus temperatures well within allowable range

• Command and Telemetry

– Flight software accepting and processing uplinked commands

• Communications

– UHF comm working nominally

0 2 4 6 8 10 12 14 16 18 10 15 20 25 30 35 Te m p e ra tu re ( d e g C ) Time (hr) Bus Temperatures Battery Avionics Payload Interface

Recent BCT Launches

– CU-Boulder LASP 3U CubeSat deployed from ISS on May 16, 2016 – 2016 Small Satellite Mission of the Year

• RAVAN (XB-3)

– 1 year mission extension

• CYGNSS (8 Nano Star Trackers & 24 p015 Reaction Wheels)

– 8 spacecraft launched on December 15, 2016 to orbit of 510 km

• IceCube (XACT)

– NASA GSFC/WPS 3U CubeSat deployed from ISS on May 16, 2017

• SHARC (XACT)

– AFRL 6U CubeSat deployed from ISS on May 17, 2017

• STP-H5 (Big Baffle Nano Star Tracker)

Future Work

• Dozens of XACT and XB-1 systems slated for numerous

missions

– Commercial, civil, DoD

– Many deep-space (with thrusters) on NASA SLS EM-1

– Delivering both systems in larger form factor for micro-sat missions

• NASA Tipping Point program driving major XACT enhancement

– Millions of dollars investment into Hyper-XACT

– Large improvements in pointing accuracy & control, radiation tolerance, performance over radiation and temperature, lifetime and reliability

– Support “operational cubesat” mission posture (lower risk, higher reliability) – Flight delivery mid-2018