J1b_7_-_PTD_Operational_Concept.pdf

Pathfinder Technology Demonstrator

Operational Concept

Small Spacecraft Technology Program Office

NASA Ames Research Center

February 9, 2016

1st Flight Demonstration

• Fly Busek MEP Thruster Payload (3 thrusters)

• Perform a thorough Spacecraft Checkout

• Perform Thrust Demo (Orbit Raise/Lower)

• Thrusters will be fired in velocity or anti-velocity vector to raise or lower orbit by accelerating or decelerating spacecraft.

Option: Globalstar Duplex Radio Tech Demo

• Fly (1) GSP-1720 Duplex Modem and Related Hardware as a Secondary

Communication System

• Exercise Globalstar to Characterize Communication System Performance

(Non-Interference to the Primary Communication System)

MEP DEMONSTRATION OPTIONS

Operational Concept (1/5)

Launch

•Powered off

•Battery capacity to survive launch delays, eclipse

•“Lazarus” mode

•ISS inhibit switch requirements (3min) and battery bypass

Deploy into

LEO

•350-800 km, any RAAN or Beta angle, (98 or 51 or 45) degree inclinations cover most available launch scenarios

•No critical event coverage assumed. Best effort to be over a station

•Wait for 45 minutes before PTD can “radiate”. Bus powers up. Survival heating available.

•If tumbling…need a mode to charge batteries (could require array deploy if no power stowed). After threshold charge reached…turn on.

Safe-Hold

•Stabilize spacecraft in a power positive “safe” mode until ground commanded. Ability to communicate.

Ground Station Contact

•Contacts scheduled with JSOC TLE’s (at least initially)

•Launch provider to provide insertion state vector.

•Assume a “beacon mode” for primary comm system. CW unmodulated tone.

Operational Concept (2/5)

Commissioning

•BUS COMMISSIONING: One week bus system commissioning. Prop system powered off. Survival power available.

•SOLAR: Auto deploy panels or cmd open.

•COMM: Step thru transceiver configurations/rates.

•ACS: HW thru attitude control scenarios to validate/calibrate control gains

•THERMAL: Monitor thermal stability, potentially adjust controls

•PROP CHECKOUT: After one week, prop system power up/checkout. Melt plug. Test communications. Measure temps, run thru voltages.

• Short duration firing to ensure no affects on other systems

• Check measurement systems – IMU, prop system measurements

System

Characterization

•Up to 23 days of propulsion system characterization (30 days total on orbit time)

• Success criteria could be met in less time

•200 hours total firing time per engine

•One monitored pass per weekday (minimum)

• 10 passes/day at 32kbps TLM (min), 2 kbps CMD (min)

• MOC staffed 4 hours/weekday= 20 hours/week

• One CMD upload/weekday

•Lights out passes everyday, remote alert notification

•Ground stations to provide data within 3 hours.

•Ground command to initiate demo

•Propulsion system to operate (at times) w/o ground contact.

Operational Concept (3/5)

Thrust Demo

Orbit

Raise/Lower

• NADIR point spacecraft

• Fire all three thrusters in the velocity/anti-velocity direction to raise/lower the orbit

• Off-Pulse the outer thrusters to counter any delta-v thrust torque bias

• Spacecraft tracks velocity vector autonomously based on GPS measurements

• GPS processed on-board (position and velocity)

• Thrust in eclipse

• Use GPS to measure orbit and characterize thrust by post processing on the ground

• NASA responsible for thrust post processing

Operational Concept (4/5)

Data

Processing

•Prop system to estimate total propellant mass usage using look up tables on the ground.

•Use mass usage w/ DV and thrust duration to estimate “effective” Isp (includes effects of pointing errors, etc.) and force.

Data

Handling

•POC (Payload Operations Center) @ GRC

•PI at Ames for commissioning, then at GRC for remainder of the mission.

•FTP or direct access to data files

•MOC / POC on the IONET

•MOC security standards met

Command

Planning

•30 day operations plan maintained

•PI to compare measure results against ground test results on a daily basis

•PI to adjust science plan as needed

•Command approval meetings to be held

Optional:

Globalstar Demo

•Power on GSP1720

•Health check of communication system

•Execute command set from MOC

•Collect Telemetry

•Note: Characterization to be performed by NASA operations personnel

Operational Concept (5/5)

Repeat - up to 23 days performance Characterization

• Burn fuel until empty or run until a thruster fails

• Option: Complete Globalstar Testing

• Exercise EOM commands Decommissioning

Deorbit 25 year maximum requirement

30 Days Total Mission Duration

Conops Big Picture – NEN Option

PTD MOC

Ames Research Center

Moffett Field, CA

GSFC

NIC

AS1

AS3

Voice

TLM / CMD / UPD

NISN

Mission Networks

IONet

- Closed

- Restricted

- Open

CMD / Acq Data

Voice

WGS

SG1

SG2

SG3

MG1 Real-Time and Stored TLM

NASA/GSFC

Ames Res Ctr

NASA/MSFC

CMD, TLM & Voice

Real-Time TLM / Redistributed Stored TLM

S-Band

Uplink:

4 kbps BPSK

Downlink:

1-2 Mbps BPSK

SC Vendor I&T Facility

S-Band

WOTIS

Sched Reqs / Acq Data

Scheds / Acq Data

TLEs

GRC

POC

TLM – Archived

USSTRATCOM

Real-Time and Stored TLM

Real-Time and Stored TLM

Real-Time and Stored TLM

Glenn Res Ctr

Activity Requests

CSAFS

Stored TLM

Redistributed Stored TLM

CMD / Acq Data

Voice

WS1

USHI01

USHI02

Real-Time TLM

AUWA01

USSTRATCOM

JSpOC

Real-Time TLM

Real-Time and Stored TLM

Voice.

CMD / Acq Data.

Internet

Stored TLM

Stored TLM

High Inclination Orbit

Low Inclination Orbit

Navigation:

TLM includes Onboard GPS Data

Spacecraft Vendor

Conops Big Picture – Vendor GDS Option

PTD MOC

Ames Research Center

Moffett Field, CA

Voice

NISN

Mission Networks

IONet

- Closed

- Restricted

- Open

Ames Res Ctr

CMD, TLM & Voice

Real-Time TLM / Redistributed Stored TLM

S-Band

Uplink:

Vendor chosen Rate

Downlink:

SC Vendor I&T Facility

RF Link

Sched Reqs / Acq Data

Scheds / Acq Data

TLEs

GRC

POC

TLM – Archived

USSTRATCOM

Real-Time and Stored TLM

Glenn Res Ctr

Activity Requests

CMD / Acq Data

Voice

USSTRATCOM

JSpOC

Any Inclination Orbit

Navigation:

TLM includes Onboard GPS Data

Spacecraft Vendor

Vendor Antenna(s)

Control Facilities

Secure Internet

(VPN, SFTP, etc)

CMD / Acq Data

Sched Reqs / Acq Data

Scheds / Acq Data

Vendor chosen Rate

Note: For Vendor supplied GDS solution, RF capabilities and GDS ground components must meet daily PTD data volume and response time requirements. Vendor is responsible for meeting FISMA security requirements and securing Spectrum authorization.

Vendor chosen

Conops Big Picture – Globalstar Option

PTD MOC

Ames Research Center

Moffett Field, CA

Voice

NISN

Mission Networks

IONet

- Closed

- Restricted

- Open

Ames Res Ctr

CMD, TLM & Voice

Real-Time TLM / Redistributed Stored TLM

S-Band

Uplink:

Vendor chosen Rate

Downlink:

SC Vendor I&T Facility

RF Link

Sched Reqs / Acq Data

Scheds / Acq Data

TLEs

GRC

POC

TLM – Archived

USSTRATCOM

Real-Time and Stored TLM

Glenn Res Ctr

Activity Requests

CMD / Acq Data

Voice

USSTRATCOM

JSpOC

Any Inclination Orbit

Navigation:

TLM includes Onboard GPS Data

Spacecraft Vendor

Vendor Antenna(s)

Control Facilities

Secure Internet

(VPN, SFTP, etc)

CMD / Acq Data

Sched Reqs / Acq Data

Scheds / Acq Data

Vendor chosen Rate

Note: For Vendor supplied GDS solution, RF capabilities and GDS ground components must meet daily PTD data volume and response time requirements. Vendor is responsible for meeting FISMA security requirements and securing Spectrum authorization.

Vendor chosen

PTD MEP Thrust Measurement Approach

Thrust Measurement Approach

Thrust in anti-velocity or velocity

• GPS update to set thrust direction (as specified by s/c)

Thrust during eclipse

Change in orbit period (semi-major axis) and argument of perigee observed

Depending on orbit altitude, on-off thrusting required to measure drag force independently

Thruster performance metrics will be determined by observing the change in the orbit parameters after extended firing.

Simulated Orbit

0 2 4 6 8 10 12 14 16 18 398.8

399.2

399.4

399.6

399.8

Time (hr)

A lt it u d e k m

• 100 uN force

• 10 kg spacecraft mass

• Initial orbit – circular, 400 km

• 1.2 km change in altitude after 16 hours

Orbit Determination Monte Carlo

Monte Carlo Simulation run to characterize orbit modeling

• GPS position/velocity measurements every minute

• 26 m 1 s, Gaussian

• Thruster on, lowering orbit

• Atmosphere known

• Harris Preister Model

• Orbit: 500 km Sun-synch

• Least squared error fit of orbit to GPS data over an orbit

• Includes thrust force and initial conditions as parameters

Thruster error over 100 cases: < 1%

Thruster characterization dominated by uncertainty in atmospheric drag