Presented to: Developed by: Presented by: Date: Federal Aviation Administration DFMC Satellite Selection Discussions IWG # 26 Jason Burns Feb 5-7, 2014 Jed Dennis and Mark Hemstad

2 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Background Legacy L1 SBAS: DO-229 –Section “The operational concept for GNSS and Space-Based Augmentation Systems is predicated on the combination of the different GNSS elements without pilot intervention. As GNSS is a global system, there should be no flight crew interaction based on airspace, so that the flight crew should not be involved in the selection of different SBASs” SARPS Section and “while the State has responsibility to approve the use of one or more SBAS signals in its airspace, due to the inability of current equipment to deselect particular SBAS, States might effectively preclude use of SBAS if the State does not approve use of all SBAS. ” –Would presence of 3-4 SBAS deter State approval?

3 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 SBAS in 2013 Minimal coverage overlap with little to no overlap in service areas SBAS Selection En Route: No selection guidance Terminal: No selection guidance Approach: SBAS identified in FAS data block

4 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Changes with DFMC –Direct avionics mitigation of ionosphere –Addition of GAGAN and SDCM –Potential to use additional core constellations Future SBAS -Results in significant regions with 3 SBAS, some regions with 4 SBAS -Overlap of coverage in SBAS Service Areas

5 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Flight Path Reference Problem GEO coverage arcs SBAS # 3 SBAS # 2 SBAS # 1 SBAS Service Areas Supported by reference network Coverage from three available SBAS Flight path through airspace of three SBAS providers Which SBAS to use when?

6 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 DFMC SBAS Selection Questions –Is SBAS selection required? Desired? DFMC capable of meeting LPV requirements in most of use area –Horizontal Alert Limit (HAL): 40 m, Vertical Alert Limit (VAL): 35 m Easily meets en route and terminal requirements –En route HAL: 2 nm; Terminal HAL: 1 nm Suggests any SBAS service would be sufficient to meet Performance Based Navigation (PBN) requirements –Assumes SBASs provide similar performance –Will future operations require tighter horizontal or vertical performance? Automated Dependent Surveillance – Broadcast (ADS-B) Trajectory Based Operations (TBO) –How well can automated selection means match SBAS Service Areas? –Will standardized selection criteria help with State approval of SBAS?

7 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 SBAS Selection Options MethodProsCons Protection Level Assessment Automated (auto), tied to capability of SBAS Requires track and decode of second SBAS provider GEO  DFRE (Clock/ephemeris covariance) Auto, measure of distance to SBAS reference network Requires track and decode of second SBAS provider GEO Maximum Common Space Vehicle (NSV) Auto, indicator of distance to SBAS reference network Undetermined regions GEO Elevation AngleAutomated and predictableInconsistent with SBAS reference network location Broadcast Service VolumeAuto, SBAS provider/State control Message downlink capacity Stored Service VolumeAuto, State ControlDatabase maintenance PreplannedAutomated, simplePilot Error and preflight work Defer to ManufacturerEnable OEM optionsUnknown behavior Pilot SelectedChange any timePilot Error and workload Broadcast Integrity Parameter Methods Pre-defined Methods

8 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Assumptions Use corrections from one SBAS at a time Select SBAS prior to GEO or ranging source selection Avionics may use any ranging source corrected by SBAS –Not required to use all corrected ranging sources SBAS selection independent of ranging source selection –Avionics able to track sufficient number of SVs corrected by SBAS –Expect can be guaranteed if any of the following are true Each SBAS broadcasts corrections for common core constellation(s) All GNSS broadcast at same frequencies (ie L1/E1 and L5/E5a) Avionics can track all core constellations

9 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Simulation Used Stanford University MAAST tool –DF mode of operations –Each SBAS run separately –Post-processed for selection assessment –Uses all in-view satellites Scenario parameters –24 1-hour time epochs –2 deg by 2 deg grid Constellations –GPS: 24 SV DO-229 MOPS constellation –Galileo: 27+3 Walker 56°:27/3/1 constellation SBAS Use Areas –Areas in which there are or expect will have SBAS Service Areas Note: Simulation results presented at ION ITM 2014

10 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Assessment Metrics SBAS selection –Percent of associated SBAS Use Area in which associated SBAS was selected every epoch –Transition Area: Percent of world in which more than one SBAS was selected over the course of a day –Predefined: Percent of associated SBAS Use Area in which designated SBAS meets availability requirements Availability –Percent of the world in which selected SBAS provided RNP 0.3 service at least 95% of the time –For pre-defined methods, percent of world in which at least one SBAS by itself provided RNP 0.3 service at least 95% of the time

11 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 HPL Selection Criteria Choose SBAS based on minimum Horizontal Protection Level Method HPL Percent of SBAS Service Area in Which the SBAS Was Selected World Availability Transition Region WAASEGNOSMSASGAGANSDCM GPS w/Galileo GPS

12 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Method NSV Percent of SBAS Service Area in Which the SBAS Was Selected World Availability Transition Region WAASEGNOSMSASGAGANSDCM GPS w/Galileo NSV Selection Criteria Choose SBAS that corrects the largest number of satellites observed by the user (Number of Common SVs) GPS

13 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 GEO Selection Criteria Choose SBAS based on highest GEO elevation angle Method GEO Percent of SBAS Service Area in Which the SBAS Was Selected World Availability Transition Region WAASEGNOSMSASGAGANSDCM GPS w/Galileo GPS

14 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014  DFRE Selection Criteria Choose SBAS based on MT-28 covariance (  DFRE) Identify SBAS that has best  DFRE for each satellite Select SBAS that has largest number of selected satellites Method δDFRE Percent of SBAS Service Area in Which the SBAS Was Selected World Availability Transition Region WAASEGNOSMSASGAGANSDCM GPS w/Galileo GPS

15 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014  DFRE, GPS and Galileo GPS GPS + Galileo Second constellation improves results Smaller transition regions Expanded Coverage

16 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Other methods Based on individual performance of SBAS in simulation Method Percent of SBAS Service Area in Which the SBAS Was Selected World Availability WAASEGNOSMSASGAGANSDCM Predefined, GPS Predefined, GPS w/Galileo Defer to Manufacturer Unknown Availability lower than best automated selection method

17 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Comparison of assessed methods –Protection Level Provides best results (SBAS selection, availability) Requires processing of multiple SBAS / GEOs –Processing requirements –Results in requirement for at least 4 GEO tracking channels »2 for Selected SBAS, 2 for alternate SBAS –δDFRE Requires sufficient number of ranging sources for positive selection Potential to improve method if prefer over protection level method –Number of common SVs Many regions lack clear selection Method requires refinement –GEO elevation angle Not for SBAS selection, okay to chose GEO once SBAS selected HPL Method seems best

18 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 SBAS Selection Options MethodProsConsRecommend Protection Level Assessment Automated (auto), tied to capability of SBAS Requires track and decode of second SBAS provider GEO Yes  DFRE (Clock/ephemeris covariance) Auto, measure of distance to SBAS reference network Requires track and decode of second SBAS provider GEO Potential if Improve Maximum Common SV (NSV) Auto, indicator of distance to SBAS reference network Undetermined regionsAcceptable GEO Elevation AngleAutomated and predictableInconsistent with SBAS reference network location No Broadcast Service VolumeAuto, SBAS provider/State control Message downlink capacityPotential Stored Service VolumeAuto, State ControlDatabase maintenancePotential PreplannedAutomated, simplePilot Error and preflight workNo Defer to ManufacturerEnable OEM optionsUnknown behaviorCurrent Standard Pilot SelectedChange any timePilot Error and workloadNo

19 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Conclusions Broadcast Integrity methods sufficient for SBAS selection –Automated, no pilot intervention –Slight improvement in availability –Protection level assessment has best performance, but other methods are close and acceptable Performance improved with more ranging satellites Trade-off between pilot responsibility, maintenance responsibility and computational burden for SBAS avionics Need to reach concurrence on methods prior to working specific requirements

Presented to: Developed by: Presented by: Date: Federal Aviation Administration Backup

21 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 SBAS Systems

22 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 VPL Selection Criteria Choose SBAS based on minimum Vertical Protection Level Method VPL Percent of SBAS Service Area in Which the SBAS Was Selected World Availability Transition Region WAASEGNOSMSASGAGANSDCM GPS w/Galileo GPS

23 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 SBAS Selection Dependency on Flight Mode Navigation Horizontal And Vertical Flight Mode SBAS Selection Per FAS data block Oceanic En-route Terminal LP LPV / LPV-200 -Requires reassessment during flight -Provide Guidance or -Manufacturer Implementation Transition to SBAS identified by FAS

24 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 SBAS Assessment Triggers Event Based –Mismatch in number of tracked versus augmented SVs Indicator of distance from SBAS Reference Stations (SRS) –Good distinction in East-West direction –Poor distinction for North-South when multiple SRS in same hemisphere –Change in longitude or latitude Set based on distance between SRS and flight speeds –Distance flown Set based on distance between SRS and flight speeds Periodic –Set time interval Set based on distance between SRS and flight speeds

25 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Constellation Selection Augmented by SBAS in use Augmented by another available SBAS Requires switching SBAS Permitted if not restricted by provider identified in FAS data block As able to support RAIM

26 Federal Aviation Administration DFMC SBAS GEO Selection – Task 2 IWG # 26, Feb 5-7, 2014 Ranging Source Selection All in view for constellation(s) in use Simplicity, does not require complex algorithm for satellite selection Best for RAIM integrity SBAS integrity uses subset with valid corrections Selection based on tracking limit of equipment Support for operation and integrity method If multi-constellation RAIM, will need an additional SV(s) to resolve constellation biases Goal is to maximize availability en-route, ensure selection of the matching service provider sufficiently before commencing final approach