1. National Aeronautics and Space Administration POIWG External Payloads Splinter: ADCO Operations Overview Ben Honey ADCO Specialist Flight Operations Directorate – CM5 Johnson Space Center Public Release Statement: This document has been reviewed for Proprietary, SBU, and Export Control (ITAR/EAR) and has been determined to be nonsensitive. It has been released to the public via the NASA Scientific and Technical Information (STI) Process DAA #33751

2. This presentation is not Export Controlled, see cover for full disclosure. Outline Motion Control System (MCS) Overview Common Operations Involving Attitude Changes Planned Increment 44-46 Events (through 2015 end) ADCO Operational Products ADCO Real-time Operations ADCO-Payloads Planning Interface ADCO / Ben Honey2

3. This presentation is not Export Controlled, see cover for full disclosure. MCS Overview ISS attitude control is performed by Control Moment Gyroscopes (CMGs), Russian Segment (RS) thruster firings, or a combination of the two. CMG Momentum Management (MM) – CMGs are used to balance and manage external torques on ISS – ISS controls to the Torque Equilibrium Attitude (TEA) – Some attitude error is allowed to keep momentum vector stable – RS thrusters available to provide desaturation firings (desats) to the CMGs CMG Attitude Hold (AH) – Tight attitude tolerances – Time-limited without thruster assist – Desats may or may not be available, depending on operation USTO (US Thrusters Only) – US segment software controls attitude using RS thrusters – CMGs do not provide attitude control torques RS Thruster Control – RS in complete attitude control of ISS – CMGs do not provide attitude control torques ADCO / Ben Honey3

4. This presentation is not Export Controlled, see cover for full disclosure. MCS Overview (cont) Attitude Knowledge vs Attitude Control Attitude knowledge error = difference between the attitude calculated by navigation sensors/software and “true” attitude Attitude control error = difference between ISS attitude as reported by nav sensors and commanded attitude Total attitude error can be considered a combination of knowledge and control error.  GNC attitude knowledge accuracy is typically within tenths of degrees of “true” attitude  CMG AH, USTO, and RS thrusters control to the commanded attitude with a higher accuracy than MM. ADCO / Ben Honey4

5. This presentation is not Export Controlled, see cover for full disclosure. MCS Overview (cont) ISS Environment Features Momentum Management does not control to a precise attitude. MM allows ISS to oscillate about the commanded attitude by up to several degrees per axis TEAs change depending on vehicle configuration. Upcoming ISS reconfig and future RS modules will change the range of TEAs that ISS will fly. ISS structure flexes. Disturbances caused by thruster firings and crew activity may impart accelerations on payload equipment. Structural deflection varies depending on location. ISS is regularly plumed by thruster firings. – ISS attitude control thrusters are located on the Service Module and Progress vehicles – Incoming and departing visiting vehicles plume ISS – both US Free-Flyers and Russian vehicles – Attached Soyuz perform a thruster test before undock, but are not used for ISS attitude control ADCO / Ben Honey5

6. This presentation is not Export Controlled, see cover for full disclosure. MCS Overview (cont) Attitude Envelopes Flight Rule B2-57 defines thermally analyzed attitude envelopes for ±XVV, ±YVV and ±ZVV attitudes ISS is required to remain within attitude envelopes unless event-specific thermal analysis is performed ISS may temporarily exceed defined envelopes when maneuvering from one attitude to another. Examples:  +XVV to –XVV during an OPM  +XVV to +ZVV for a Progress docking ISS may stay in –XVV for hours to days at a time YVV and ZVV attitudes typically only for a few hours ADCO / Ben Honey6 Reference Frames ADCO monitors and controls ISS attitude in LVLH GPS calculates ISS attitude and state vector in CTRS Some GNC calculations are performed in Inertial/J2000

7. Reference Frame Visualizations Ecliptic Mean Equator Mean Vernal Equinox X Y Z Mean Rotational Axis Jan. 1, 2000, Noon Inertial / J2000 Z CTRS Prime Meridian X CTRS Y CTRS TOD Equator CIO Rotational Axis CIO (Conventional International Origin) Conventional Terrestrial Reference System (CTRS) Z LVLH X LVLH Y LVLH Z LVLH X LVLH Y LVLH LVLH

8. This presentation is not Export Controlled, see cover for full disclosure. Common Operations Russian Visiting Vehicle Dockings/Undockings – +XVV,-XVV, +ZVV, -ZVV attitudes all possible – Typically performed on RS thruster control, but Progress aft undockings and some Soyuz undockings are now being performed on CMG MM Optimal Propellant Maneuvers – Maneuver between +XVV and –XVV using USTO – Follows optimized trajectory to utilize gravity gradient torques and reduce prop consumption – not a pure single-axis maneuver Free-Flyer Capture/Release (Dragon, Cygnus, HTV) – Small USTO maneuvers to and from capture/release attitudes – Short period of CMG AH with thrusters inhibited for Free-Flyer capture with SSRMS Reboosts – RS thruster burn using SM main engine or Progress thrusters to increase altitude, decrease altitude, or for debris avoidance maneuver (DAM) These types of “thruster hold” events typically last for a few hours ADCO / Ben Honey8

9. This presentation is not Export Controlled, see cover for full disclosure. Common Operations (cont) RS EVAs – Russian EVAs require RS thruster control hold for DC1 airlock depress. – Once crew has egressed, control can be returned to US MM – If EV crew is within keep-out-zone of Progress or SM thrusters, thrusters must be inhibited US EVAs – US EVAs can occur on US MM – Loading constraints may dictate need for thruster inhibits, depending on activities being performed – EVAs outboard of SARJs may require +/-YVV attitude Thruster Disables – In addition to previously listed events, numerous operations require thruster inhibits, including: SSRMS and SPDM robotic operations, RS vehicle clamp install/removal, free-flyer vehicle install/uninstall, and JEMRMS operations ADCO / Ben Honey9

10. This presentation is not Export Controlled, see cover for full disclosure. Increment 44-46 Dynamic Events ADCO / Ben Honey10 EventControl TypeAttitude OPM to -XVVUSTO+XVV to -XVV 43S DockRS Thrusters-XVV OPM to +XVVUSTO-XVV to +XVV A/L depress RS EVA 41CMG AH+XVV 58P Prop Line PurgeCMG AH+XVV 58P undockCMG MM+XVV HTV-5 Capture USTO/CMG AH+XVV 42S Thruster TestRS Thrusters+XVV 42S RelocateRS Thrusters+XVV OPM to –XVVUSTO+XVV to –XVV 44S DockRS Thrusters-XVV OPM to +XVVUSTO-XVV to +XVV

11. This presentation is not Export Controlled, see cover for full disclosure. Increment 44-46 Events (cont) ADCO / Ben Honey11 EventControl TypeAttitude 42S Thruster TestRS Thrusters+XVV 42S UndockCMG MM+XVV OPM to –XVVUSTO+XVV to –XVV 61P DockRS Thrusters-XVV OPM to +XVVUSTO-XVV to +XVV HTV-5 Release USTO/CMG AH+XVV 60 Prop Line PurgeCMG MM+XVV 60P Undock USTO/RS Thrusters+ZVV -XLV 62P Dock RS Thrusters+XVV Cygnus-4 Capture USTO/CMG AH+XVV 61P Prop Line Purge CMG AH+XVV 61P Undock CMG MM+XVV

12. This presentation is not Export Controlled, see cover for full disclosure. Events still awaiting details from FPIP or DEWG (as of July 8) ADCO / Ben Honey12 EventControl TypeAttitude SpaceX-8 USTO/CMG AH+XVV SpaceX-9 USTO/CMG AH+XVV 43S RelocateTBD 45S DockTBD 43S Undock TBD FPIP = Flight Planning Integration Panel sets the flight plan (ie, when are vehicles coming and going) DEWG = Dynamic Events Working Group determine things like docking attitude, thruster configuration, solar array angles. All very dependent on environmental factors like sun angle, orbit phasing, etc.

13. This presentation is not Export Controlled, see cover for full disclosure. ADCO Operational Products ADCO maintains products on the MCS Flight Info website. – Access to MCC Gateway and MCS Flight Info may be restricted. The ATL and MCS Flight Info can be accessed from MCC Gateway: ADCO / Ben Honey13

14. This presentation is not Export Controlled, see cover for full disclosure. ADCO Operational Products (cont) The Attitude Timeline (ATL) shows all upcoming events involving changes to MCS configuration Operations are typically listed in the ATL at E-30 days Information listed: – Time of event – Attitude name – Reference Frame – Commanded attitude – From/To Config* – Event and remarks *F/T Config decoder in backup slides ADCO / Ben Honey14

15. This presentation is not Export Controlled, see cover for full disclosure. ADCO Real-time Operations ADCO responsibilities include: Monitor overall health of the MCS – Navigation accuracy – Attitude control performance – ORU health and status Integration of MCS with other ISS systems during nominal operations and failure response Coordinate planning of future MCS activities with MCC-H and MCC-M teams Determine constraints impacting MCS and plan/execute operations accordingly – Thruster configurations and inhibits – Solar array constraints – Loads constraints during robotics, payloads, and EVA operations Execute MCS operations to achieve Increment goals Monitor numerous voice loops with focus on MCC-H activities – ADCO can communicate with POIC through PRO, OC, or POD – ADCO can be contacted on ADCO 1 or FCR SYS 1 ADCO / Ben Honey15

16. This presentation is not Export Controlled, see cover for full disclosure. ADCO-Payloads Planning Interface ADCO wants to know who is planning around MCS To make Flight Director aware of all immediate impacts in a contingency To make community aware of special operations that require expert knowledge to realize there is a thruster firing risk Examples of hardware with thruster firing constraints: – USOS windows – USOS isolated exercise equipment – FIR and CIR payloads – JAXA Marangoni experiment What would we do with that information? Add your safing steps to our contingency procedures Avoid unnecessarily impacting Earth-observing science from the windows Use your constraint as justification for more flexible MCS ops concepts ADCO / Ben Honey16

17. This presentation is not Export Controlled, see cover for full disclosure. ADCO-Payloads Planning Interface How do you know if there is a thruster event? Long-range (1-6 months) – FPIP graphic or DEWG table* Medium range (1-4 weeks) - Attitude Timeline (ATL)* Short range (less than 1 week) – ATL and OSTPV How you can impact the plan OIP 7.5.4 ISS Attitude Change or Microgravity Request to submit Request for Attitude Change (RAC) Example: ESA’s SOLAR payload used this process to request yaw-biased attitude for summer and winter solstice sun observation A RAC can also be used to request a period of microgravity ops How much lead time on a request? ADCO’s goal is to have MCS operations in the ATL at E-30 days Thruster inhibits can be added later if necessary (up to ~E-7 days) The OIP states 3 weeks if within approved attitude envelope, 4 weeks out of envelope However, more lead time is recommended, to ensure that any issues (such as analyzing controllability of your attitude request) can be resolved A revision to this process is likely if more users are found *reboosts are not planned by DEWG; likely not be known until medium-range timeframe ADCO / Ben Honey17

18. This presentation is not Export Controlled, see cover for full disclosure. Q&A ADCO / Ben Honey18

19. This presentation is not Export Controlled, see cover for full disclosure. ATL F/T Config Decoder ADCO / Ben Honey19

20. This presentation is not Export Controlled, see cover for full disclosure. MCS Flight Info ADCO / Ben Honey20 Links include: Current ATL Backup ATL Same format as ATL, but for contingency events As-Flown ATL MCS Ops Timeline Thruster Reconfiguration Timeline (TRTL) Contingency TRTL As-Flown TRTL Prop Consumption Spreadsheet RAC form and database TOPO Data File Access to MCS Flight Info and associated links may be restricted.

21. This presentation is not Export Controlled, see cover for full disclosure. RAC description from OIP 7.5.4 ADCO / Ben Honey21 “It may be necessary for payload customers and IPs to request changes to the ISS agreed-to attitude plan. Additionally, this form should be used to request periods of microgravity. While the justification for these changes will come through the Program Office or relevant management decisions, the process for implementing these changes is documented below. The output from this procedure will flow into the Attitude Change Request (ACR) process between the MCC-H FCT and ГОГУ (OIP Volume A: NASA/Roscosmos, Section A7.5.4). Request for Attitude Change (RAC) forms should be submitted no later than 4 weeks prior to the activity if the requested attitude is outside the approved attitude envelope. This will allow time for the CHIT to be processed. If the requested attitude is within the approved attitude envelope, the RAC form should be submitted no later than 3 weeks prior to the activity.”