MSO-C145a_GPS.pdf

Department of Defense GPSWing

User Systems Engineering Los Angeles AFB, CA

I MSO-C145a I

Date: 11 , February, 2010

Military Standard Order

Subject: MSO-C145, AIRBORNE NAVIGATION SENSORS USING THE

GLOBAL POSITIONING SYSTEM (GPS) I PRECISE

POSITIONING SERVICE (PPS) FOR AREA NAVIGATION

(RNA V) IN REQUIRED NAVIGATION PERFORMANCE (RNP)

AIRSPACE; RNP-20 RNA V THROUGH RNP-0.3 RNA V

Approved by

MICHAELJ. DUNN, DISL, DAF

Technical Director Global Positioning Systems Wing

Report Documentation Page Form Approved OMB No. 0704-0188

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1. REPORT DATE

11 FEB 2010 2. REPORT TYPE

3. DATES COVERED

00-00-2010 to 00-00-2010

4. TITLE AND SUBTITLE

MSO-C145, Airborne Navigation Sensors Using The Global Positioning System (GPS) / Precise Positioning Service (PPS) For Area Navigation (RNAV) In Required Navigation Performance (RNP) Airspace; RNP-20 RNAV Through RNP-0.3 RNAV

5a. CONTRACT NUMBER

5b. GRANT NUMBER

5c. PROGRAM ELEMENT NUMBER

6. AUTHOR(S) 5d. PROJECT NUMBER

5e. TASK NUMBER

5f. WORK UNIT NUMBER

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

Department of Defense,GPS Wing,User Systems Engineering,Los Angeles

AFB,CA,90009

8. PERFORMING ORGANIZATION

REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S)

11. SPONSOR/MONITOR’S REPORT

NUMBER(S)

12. DISTRIBUTION/AVAILABILITY STATEMENT

Approved for public release; distribution unlimited

13. SUPPLEMENTARY NOTES

14. ABSTRACT

15. SUBJECT TERMS

16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF

ABSTRACT

Same as

Report (SAR)

18. NUMBER

OF PAGES

19a. NAME OF

RESPONSIBLE PERSON

a. REPORT unclassified

b. ABSTRACT unclassified

c. THIS PAGE unclassified

Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18

Subject: MSO-C145, AIRBORNE NAVIGATION SENSORS USING THE

GLOBAL POSITIONING SYSTEM (GPS) / PRECISE

POSITIONING SERVICE (PPS) FOR AREA NAVIGATION

(RNAV) IN REQUIRED NAVIGATION PERFORMANCE (RNP)

AIRSPACE; RNP-20 RNAV THROUGH RNP-0.3 RNAV

DISTRIBUTION: SMC/GP (3 cys); AFFSA, NAWCAD, ESC/GA; SSC SD Code 231;

CECOM; PMW 170

Department of Defense GPS Wing

User Systems Engineering Los Angeles AFB, CA

MSO-C145a

Date: 11, February, 2010

Military Standard Order

1. PURPOSE. This Military Standard Order (MSO) prescribes the minimum performance standards that airborne area navigation sensors using the Global Positioning System (GPS) / Precise Positioning Service (PPS) must meet to be identified with the applicable MSO marking.

The similarity of this MSO with Technical Standard Order (TSO) C-145, "Airborne Navigation Sensors using the Global Positioning System (GPS) augmented by the Wide Area Augmentation System (WAAS)", is intentional.

2. APPLICABILITY. The standards of this MSO apply to equipment intended to provide position information to a navigation management unit that provides appropriate flight path, planning, outputs supporting guidance commands enabling pilot flight path tracking, navigation status/progress, and positional/situational awareness. These capabilities are essential to the conduct of operations in Required Navigation Performance (RNP) airspace. These standards do not address integration issues with other avionics, such as the potential for the sensor to inadvertently command an autopilot hardover or the suitability of the sensor for use in a multi-sensor navigation suite. These standards also do not address the use of position information for other applications such as automatic dependent surveillance.

3. SUBSTITUTION. Airborne navigation sensors identified with the MSO-C145a marking can substitute for airborne navigation sensors identified with a TSO-C145 marking in RNP-20 through RNP-0.3 area navigation (RNAV) operations, but are not acceptable substitutes in precision approach operations. (The precision approach functions required of TSO-C145 marked airborne navigation sensors for vertical navigation are not required of MSO-C145a marked airborne navigation sensors.) Airborne navigation sensors identified with the MSO-C145a marking are also acceptable substitutes for airborne navigation sensors identified with a TSO- C129 Class B() or TSO-C129a Class B() marking in RNP-20 through RNP-0.3 RNAV operations.

NOTE: Airborne navigation sensors identified with the MSO-C145a marking are required to provide vertical navigation (VNAV) performance only to the extent specified in Section 4 below. The specified level of VNAV performance is not intended to support VNAV or precision approach operations in RNP airspace. It is expected that these operations will be conducted using barometric altimetry.

4. REQUIREMENTS. Airborne navigation sensors using PPS that are to be so identified must meet the minimum performance standards for Class Beta-1 and Class Beta-2 equipment set forth in Section 2 of RTCA/DO-229B, “Minimum Operational Performance Standards for Global Positioning System/Wide Area Augmentation System Equipment”, dated 6 October 1999 except as specified herein. MSO-C145a marked airborne navigation sensors are not required to meet the minimum performance standards for Class Beta-3 equipment, or Class Gamma equipment, or Class Delta equipment. Class Beta-1, Class Beta-2, and Class Beta-3, Class Gamma, and Class Delta equipment are defined in Section 1 of RTCA/DO-229B. Operation with GNSS elements other than GPS is not required.

a. Failure Condition Classification. Failure of the function defined in paragraph 2 of this MSO has been determined to be a major failure condition for loss of function and malfunction of en route, terminal, or non-precision approach position data. The applicant must develop the system to at least the design assurance level commensurate with this hazard classification.

b. Exceptions to RTCA/DO-229B.

(1) Precedence. In the event of a conflict between the performance requirements or conditions imposed by the prime item specification for the GPS/PPS navigation sensor and the performance requirements or conditions imposed by this MSO through the invocation of RTCA/DO-229B, the precedence of the performance requirements or conditions shall be as follows. If the performance requirements or conditions imposed by the prime item specification are more rigorous or stringent than the requirements or conditions imposed by this MSO, then the performance requirements or conditions imposed by the prime item specification shall take precedence, unless otherwise explicitly specified in this MSO. However, if the prime item specification requirements or conditions do take precedence, those performance requirements or conditions do not necessarily need to be met in order to be identified with the applicable MSO marking (e.g. see paragraph 6a(13).

(2) Equipment Performance and Test Procedure Deletions. The following paragraphs and Sections of RTCA/DO-229B are not required for equipment certified to Class Beta-1 or to Class Beta-2 requirements: 2.1.1.3, 2.1.1.4, 2.1.1.5.2 through 2.1.1.5.4, 2.1.1.8.2, 2.1.2.2.2.1, 2.1.3.2.2.1, 2.1.3.7 through 2.1.3.9, 2.1.4, 2.2, 2.3, 2.5.2, 2.5.9.3.3.1, 2.5.10, and 2.5.11.

(3) Installed Equipment Performance Deletions. The following paragraphs and Sections of RTCA/DO-229B will not be required for installations of equipment certified to Class Beta-1 or to Class Beta-2 requirements: 3.3 and 3.4. The remainder of Section 3 shall be addressed in the equipment installation procedure and limitations (see 6.a.(2) of this MSO).

(4) Appendix Deletions. The following appendices of RTCA/DO-229B are not required for equipment certified to Class Beta-1 or to Class Beta-2 requirements: Appendix A except for Section A.4.2.4, Appendix D, Appendix F, Appendix H, Appendix J, Appendix P, and Appendix Q. It is noted that paragraph 1.1 of RTCA/DO-229B defines Appendices M through O as being informative rather than normative.

(5) GPS/PPS vice GPS/WAAS. Substitute "GPS/PPS" for all references to "GPS/WAAS" and/or "WAAS" in RTCA/DO-229B since the ability to use WAAS signals is not required (e.g., Substitute "GPS/PPS positioning" for "GPS/WAAS positioning", "GPS/PPS navigation" for "GPS/WAAS navigation”, etcetera).

(6) PPS-Based vice WAAS-Based. Substitute "PPS-based" for all references to "WAAS-based" in RTCA/DO-229B since the ability to use WAAS signals is not required.

(7) WAAS Satellites, WAAS Signals, Etcetera. Delete all references to WAAS satellites, WAAS signals, WAAS data, WAAS corrections, WAAS information, WAAS coverage area, etcetera in RTCA/DO-229B since the ability to use WAAS signals is not required.

(8) HPLWAAS and VPLWAAS. Delete all references to the Horizontal Protection Level computed using WAAS (HPLWAAS) and the Vertical Protection Level computed using WAAS (VPLWAAS) in RTCA/DO-229B since the ability to use WAAS signals is not required.

(9) PPS Simulator vice GPS/WAAS Simulator. Substitute "GPS/PPS signal generator (simulator)" for all references to "GPS/WAAS signal generator (simulator)" in RTCA/DO-229B since the ability to use WAAS signals is not required.

(10) Precision Approach. Delete all references to precision approach, specifically including but not limited to Category I precision approach in RTCA/DO-229B since the ability to support precision approach is not required for equipment certified to Class Beta-1 or Class Beta-2 requirements.

(11) Primary (Sole) Means. Substitute "primary means" for all references to "primary (sole) means" in RTCA/DO-229B since sole means is not an objective for PPS.

(12) SPS Signal Specification References. Substitute a reference to IS-GPS-200 (i.e., "Ref. IS-GPS-200") in lieu of all references to specific paragraphs of the main body of the SPS Signal Specification in RTCA/DO-229B since IS-GPS-200 is the governing document for GPS signal-in-space technical details.

(13) System Overview. In lieu of the information in paragraph 1.2 of RTCA/DO-229B, substitute the following information:

"GPS provides two defined levels of positioning service: (1) the Precise Positioning Service (PPS), and (2) the Standard Positioning Service (SPS). When employed as described herein, the PPS is sufficient to serve as the basis for Area Navigation (RNAV) in Required Navigation Performance (RNP) airspace for RNP-20 through RNP-0.3 RNAV operations.

In the event that the PPS cannot be accessed, either because the GPS/PPS equipment lacks the requisite cryptographic keys ("PPS keys") or because of an operator-commanded PPS lock out (see Section 2.1.1.2), the SPS is used as the basis for RNAV in RNP airspace for RNP-20 through RNP-0.3 RNAV operations subject to local Air Traffic Control (ATC) regulation."

(14) Wide Area Augmentation System. In lieu of paragraph 1.2.1 of RTCA/DO-229B, substitute the following placeholder: "Reserved."

(15) GPS Signal Characteristics. Add the following information to paragraph 1.2.2.1 of

RTCA/DO-229B:

"Another PRN code, either known as the Precise (P) code or its encrypted alternative, known only as the Y code, is generated at a rate of 10.23 MHz and modulated onto both the GPS L1 frequency and onto the GPS L2 frequency (1227.6 MHz). All GPS satellites transmit at the same L1 and L2 frequencies. The carriers are modulated with a specific C/A code and a specific P(Y) code for each GPS satellite.

"Detailed PPS information is provided in the GPS PPS Performance Standard, Edition 1.

"GPS signal-in-space technical details, for both the PPS and the SPS, are provided in IS- GPS-200D, 7 December 2004, including IRN-200D-001, 7 March 2006."

(16) Figure 1-1. In lieu of Figure 1-1 of RTCA/DO-229B, substitute the following placeholder: "Reserved."

(17) WAAS Signal Characteristics. In lieu of paragraph 1.2.2.2 of RTCA/DO-229B, substitute the following placeholder: "Reserved."

(18) Operational Goals. In lieu of the information in paragraph 1.3 of RTCA/DO-229B, "The operational goal of GPS/PPS equipment certified to Class Beta-1 or to Class Beta-2 requirements is to be able to serve as the only radionavigation equipment required onboard the aircraft to meet RNP RNAV requirements for oceanic, remote area and domestic en route, terminal and non-precision approach phases of flight.

"Additional goals for PPS are to provide:

a) flexibility for future enhancements;

b) truly seamless worldwide radionavigation;

c) positioning and time for automatic dependent surveillance;

d) ground movement monitoring (with augmentation);

e) growth to GPS / Joint Precision Approach and Landing System (JPALS) /

Local Area Augmentation System (LAAS) for Category I, II, and III precision approach;

f) secure and reliable navigation in the presence of interference (accidental and/or intentional); and

g) replacement of other radionavigation systems."

(19) International Compatibility. In lieu of paragraph 1.3.3 of RTCA/DO-229B, "The operational concept for the GPS/PPS is as a truly seamless worldwide source of radionavigation. As such, there should be no need for flight crew interaction based on airspace so that the flight crew should not normally have to select any other radionavigation service for RNP-20 through RNP-0.3 RNAV operations anywhere in the world.

" It is recognized that authorities in certain nations may choose to not allow GPS/PPS-based navigation or any GPS-based navigation in airspace under their control. In airspace regions where no GPS-based navigation is allowed, GPS/PPS equipment will necessarily be superfluous. In those airspace regions where GPS-based navigation is allowed but not GPS/PPS-based navigation (i.e., GPS/SPS-based navigation only), GPS/PPS equipment can still be used provided that certified equipment is able to access and operate using only the SPS. To accommodate such national peculiarities, GPS/PPS equipment will be required to incorporate an operator-commanded lock out capability which limits the equipment to employing only the SPS signals for positioning functions. The lock out capability will provide a SPS-based receiver which meets or exceeds civil standards (e.g. TSO-C129a, FAA Notice 8110.60, EUROCONTROL 003-93). See Section 2.1.1.2 for requirements applicable to this operator-commanded PPS lock out capability.

"Although the ability to use WAAS signals is not required in MSO-C145a marked airborne navigation sensors, the ability to use WAAS signals is not prohibited in MSO-C145a marked airborne navigation sensors. The ability to use Space-Based Augmentation System (SBAS) signals, such as from WAAS satellites, may provide additional international compatibility in certain airspace where the controlling authority has chosen to require the use of particular SBAS signals for specific operations. For example, the use of European Geostationary Navigation Overlay Service (EGNOS) signals could be declared as mandatory for RNP-0.3 RNAV operations at a certain airport by the State responsible for that airport due to local signal monitoring considerations. MSO-C145a marked airborne navigation sensors are allowed to incorporate abilities to use SBAS signals as an option;

however, all MSO-C145a marked airborne navigation sensors are required to meet the requirements specified herein without the use of SBAS signals. Additionally, to avoid any risk of compromising the military utility of PPS, the ability to use SBAS signals is not permitted when the equipment is operating in the keyed PPS mode or when the use of the particular SBAS signal or signals has not been intentionally selected by the operator. See paragraph 2.1.1.2.4 for requirements applicable to this optional operator-selected "SBAS use permitted" capability."

(20) Aiding and Multiple Sensors. Replace the information relating to the use of barometric altitude for the fault detection and exclusion (FDE) algorithm in paragraph 1.5 of RTCA/DO-229B as follows.

Delete the existing text which reads:

"Although it is not required, the use of barometric altitude for the fault detection and exclusion (FDE) algorithm is highly recommended. Baro-aiding can significantly improve the system availability outside of the WAAS service volume (for the en route, terminal area, and non-precision approach phases of flight, FDE is only required when the WAAS is not providing integrity). Implementations which provide increased availability may be used and may obtain operational benefits in areas outside the WAAS service volume."

Insert new text which reads:

"The ability to use barometric altitude inputs for both the fault detection and exclusion (FDE) algorithm and the position fixing algorithm is required since baro-aiding can improve GPS/PPS-based RNP RNAV availability for en route, terminal area, and non-precision approach phases of flight when these functions cannot be provided by the satellites alone.

Barometric altimeter aiding is used in the FDE algorithm to provide integrity and continuity, and in the position-fixing algorithm to maintain horizontal accuracy only when these functions cannot be provided by the satellites alone. Appendix G describes the minimum requirements and test procedures for barometric altimeter aiding. Alternative implementations which provide increased availability may be used and may obtain improved operational benefits."

(21) GPS Constellation. In paragraph 1.8.1.1, substitute a matched pair of references that reads as "GPS PPS Performance Standard, Edition 1, February 2007 and the GPS SPS Performance Standard, Edition 4, September, 2008" in lieu of the existing references to "GPS SPS Signal Specification, dated June 2, 1995".

(22) RF Interference. In lieu of paragraph 1.8.1.7 of RTCA/DO-229B, substitute the following information:

"It is assumed that this document's specification of the RF signal environment (Appendix C) in which GPS/PPS navigation sensors must operate successfully during unkeyed PPS mode operations or during PPS lock out mode operations will be consistent with the real environment experienced while operating in those modes. Furthermore, it is also assumed that the RF signal environment specified in the prime item specification for the GPS/PPS navigation sensor in which the GPS/PPS navigation sensor must operate successfully during keyed PPS mode operations will be consistent with the real environment experienced while operating in the keyed PPS mode."

(23) Time of Applicability of the WAAS Signal-in-Space. In lieu of paragraph 1.8.1.8 of RTCA/DO-229B, substitute the following placeholder: "Reserved."

(24) Change of Broadcast Ephemeris. In lieu of paragraph 1.8.1.9 of RTCA/DO-229B, substitute the following placeholder: "Reserved."

(25) WAAS Regional Message Type (Message Type 27). In lieu of paragraph 1.8.1.10 of RTCA/DO-229B, substitute the following placeholder: "Reserved."

(26) Precision Approach Applications. In lieu of Section 1.8.2 of RTCA/DO-229B, substitute the following placeholder: "Reserved."

(27) GPS Signal Processing Requirements. In lieu of the requirements in paragraph

2.1.1.2 of RTCA/DO-229B, substitute the following requirements:

"GPS/PPS equipment shall be designed to process the GPS signals and necessary data described in the GPS PPS Performance Standard under interference conditions specified in Appendix C for L1 operation, and under the minimum signal conditions defined in Section

2.1.1.10. For L2 operation the interfering CW signals are the same as for L1, but offset in frequency. The minimum signals for PPS L1 and L2 should be suitably adjusted for relative satellite signal level. GPS/PPS equipment shall also be designed to process the GPS signals and necessary data described in the GPS SPS Performance Standard under interference conditions described in Appendix C and under the minimum signal conditions defined in Section 2.1.1.10. If dual-frequency ionospheric corrections are not applied to a pseudorange, then the equipment shall decode the ionospheric coefficients in the GPS navigation message and apply the ionospheric corrections described in IS-GPS-200. If dual-frequency ionospheric corrections are applied to a pseudorange, then the GPS ionospheric model shall not be used for that satellite. A tropospheric correction shall be applied (an acceptable algorithm is described in Appendix A, Section A.4.2.4).

"GPS satellite navigation data shall be continuously decoded while code and carrier track is maintained.

"In addition, the equipment shall not mistake one GPS satellite for another due to cross-correlation during acquisition or reacquisition. An acceptable means of preventing cross-correlation from causing a false range is to reject GPS satellite ranging data if there is a greater than 3000 km separation between satellite positions derived from the almanac and broadcast ephemerides.

"The GPS/PPS equipment shall be designed to operate in at least the following three GPS signal processing modes. GPS/PPS equipment which is unable to operate in the Operator-commanded PPS lock out mode may still be eligible for identification with the applicable MSO marking provided a deviation or waiver authorizing the omission is granted; see paragraph 6 of this MSO.

a) Keyed PPS mode;

b) Operator-commanded PPS lock out mode; and

c) Unkeyed PPS mode."

The following table represents the GPS signal processing capability for each of the equipment operating modes:

Table 1: Equipment Operating Modes and Corresponding Signal Process Capabilities

SIGNALS

MODES L1 C/A L1 P L1 P(Y) L2 C/A L2 P L2 P(Y)

Keyed PPS X X X X X X

PPS-LO X

Unkeyed PPS X X X X

(28) GPS Signal Processing Mode Requirements. Add the following requirements to paragraph 2.1.1.2 of RTCA/DO-229B (as modified above) to thereby produce an entirely new paragraph 2.1.1.2 with 4 subparagraphs:

"2.1.1.2.1 Keyed PPS Mode The primary GPS/PPS equipment operating mode shall be keyed PPS mode. Whenever the equipment has been keyed with valid PPS keys, the equipment shall operate in the keyed PPS mode unless otherwise commanded by the operator or the equipment fails to track at least one Y-code signal. In the keyed PPS mode, all GPS related information shall be derived exclusively from the PPS signals as described in the GPS PPS Performance Standard, Edition 1, except during acquisition or reacquisition as allowed for by the prime item specification for the PPS navigation sensor. If MSO Approved Government Furnished Equipment (GFE)/Government Furnished Information (GFI) Parts List (MAGPL) items are installed and the GPS/PPS equipment is operating in keyed-PPS mode, unless at least one Y-code signal is tracked, no data from the GFE/GFI, pertinent to PPS URA, dither, and epsilon calculations shall be used to generate the solution of position, velocity, time, or integrity.

"2.1.1.2.2 Operator-Commanded PPS Lock Out (PPS-LO) Mode When specifically commanded by the operator (or commanded by an external system in lieu of an operator), GPS/PPS equipment operating in Keyed PPS mode shall transition to operating in the operator-commanded PPS lock out (PPS-LO) mode. In the PPS-LO mode, all GPS related information shall be derived exclusively from the L1 C/A-code signal as described in the GPS SPS Performance Standard. Commanding the PPS-LO mode differs from commanding the zeroization of the PPS keys since the PPS keys shall not be zeroized in response to the PPS-LO mode command. The PPS keys shall be retained in the PPS-LO mode and the equipment shall continue to function as a PPS receiver with all required capabilities enabled except for deriving all position related information exclusively from the L1 C/A-code signal (i.e., no classified selective availability (SA) processing applied and no classified anti-spoofing (A-S) techniques employed). The use of classified SA processing and/or classified A-S techniques for functions other than deriving the output position related information is not precluded. When the PPS-LO mode is de-commanded by the operator, the equipment shall revert back to operating in Keyed PPS mode. The transitions from Keyed PPS mode to PPS-LO mode, and from PPS-LO mode to Keyed PPS mode, assuming that the receiver is properly keyed, shall be accomplished within 8 seconds of operator command or de-command. As an option, the PPS equipment may provide an operator-selected SBAS use permitted submode under the PPS-LO mode; see paragraph 2.1.1.2.4.

GPS/PPS equipment which is unable to operate in the PPS-LO mode pursuant to a deviation or waiver (see paragraph 6 of this MSO) may incur operational restrictions that preclude access to certain airspace. GPS/PPS equipment should ignore signals other than L1 C/A in the PPS-LO mode. If MSO Approved GFE/GFI Parts List (MAGPL) items are installed and the GPS/PPS equipment is operating in PPS-LO mode, no data from the GFE/GFI, pertinent to PPS URA, dither, and epsilon calculations shall be used to generate the solution of position, velocity, time, or integrity.

“Note: In the Operator Commanded PPS Lock Out mode, if the GPS/PPS equipment can control a CRPA with switchable L1 or L2 nulling capability, the nulled frequency should focus on L1 not L2.

"2.1.1.2.3 Unkeyed PPS Mode The equipment shall operate in, or transition to, Unkeyed PPS mode under the following conditions:

1. The equipment has not been keyed with valid PPS keys, or

2. The equipment has zeroized its keys, or

3. While operating in Keyed PPS mode, the equipment fails to track at least 1 Y-code signal, or

4. While operating in Keyed PPS mode and the equipment detects a failure of the MSO

Approved GFE/GFI Parts List (MAGPL) item(s) (if installed).

As an option, the equipment may provide an operator-selected SBAS use permitted submode under the unkeyed PPS mode; see paragraph 2.1.1.2.4.

“Note: This mode is not the SPS mode. If a satellite is transmitting P-code or C/A-code on

L2, the GPS/PPS equipment operating in unkeyed PPS mode should have the capability to track these codes (see Table 1: Equipment Operating Modes and Corresponding Signal Processing Capabilities).

"2.1.1.2.4 Operator-Selected SBAS Use Permitted (SBAS-UP) Submode As an option, GPS/PPS equipment may provide an operator-selected SBAS Use Permitted (SBAS-UP) submode under the PPS-LO mode and/or the unkeyed PPS mode. If the GPS/PPS equipment provides an SBAS-UP submode, it shall not be accessible from the keyed PPS mode. The SBAS-UP submode, if provided, shall comply with the SBAS and WAAS related requirements specified in TSO-C145. In the event of conflict between the PPS, PPS-LO, or SPS related requirements specified herein and the SBAS and WAAS related requirements specified in TSO-C145, the requirements specified herein shall take precedence except when operating in the SBAS-UP submode."

(29) Satellite Integrity Status. In lieu of the requirements in paragraph 2.1.1.5 of RTCA/DO-229B, substitute the following requirements:

"The GPS/PPS equipment shall designate each GPS satellite as GPS UNHEALTHY or as GPS HEALTHY as defined in paragraphs 2.1.1.5.5 and 2.1.1.5.6. The latency of this designation must be consistent with the requirements of Section 2.1.1.13."

(30) GPS UNHEALTHY Designation. Replace the requirement relating to Bit 18 of the HOW in paragraph 2.1.1.5.5 of RTCA/DO-229B as follows.

Delete the existing text which reads:

"- Bit 18 of the HOW is set to 1 (Ref. 2.4.2.2 of the GPS SPS Signal Specification);"

Insert new text which reads:

"- Bit 18 of the HOW is set to 1 (Ref. IS-GPS-200) and the equipment is operating in either the PPS-LO mode or the unkeyed PPS mode;"

(31) GPS UNHEALTHY Designation. Add the following requirement to paragraph

2.1.1.5.5 of RTCA/DO-229B:

Insert new text which reads:

"- Additionally, GPS Satellite shall be declared UNHEALTHY when the step detector function has declared a step error."

(32) Satellite Selection. In lieu of the requirements in paragraph 2.1.1.6 of RTCA/DO- 229B, substitute the following requirements:

"The GPS/PPS equipment shall automatically select satellites for use in the position fixing algorithm and in the FDE algorithm. As necessary to maintain an accurate position fix, maintain a reliable fault detection capability, and -- when a fault has been detected --provide reliable fault exclusion, the minimum satellite mask angle shall be no greater than 2 degrees in keyed PPS mode. If an accurate position fix cannot be maintained and/or a reliable fault detection capability cannot be maintained and/or -- when a fault has been detected -- reliable fault exclusion cannot be provided using all GPS HEALTHY satellites above the minimum satellite mask angle, then barometric altimeter aiding (if made available by aircraft to the GPS/PPS equipment) shall be used as necessary to maintain an accurate position fix, maintain a reliable fault detection capability, and -- when a fault has been detected -- provide reliable fault exclusion. See paragraph 1.5. Appendix G describes the minimum requirements and test procedures for barometric altimeter aiding.

"Note: Alternative implementations which provide increased availability may be used by the manufacturer provided they do not compromise accuracy or integrity."

(33) Sensitivity and Dynamic Range. In lieu of the requirements in paragraph 2.1.1.10 of RTCA/DO-229B, substitute the following requirements:

"The sensitivity and dynamic range of the GPS/PPS equipment shall be as specified in the prime item specification for the GPS/PPS navigation sensor. Manufacturers are encouraged, but are not required, to design the GPS/PPS equipment to be interoperable with one or more of the standard GPS/PPS antennas as specified in MSO-C144.

"Note: The receiver manufacturer should indicate in the prime item specification, the associated interface documentation, or in the installation instructions what type(s) of antenna the equipment is interoperable with and the maximum and minimum tolerable losses for installation with that type of antenna."

(34) Figure 2-2. In lieu of Figure 2-2 of RTCA/DO-229B, substitute the following placeholder: "Reserved."

(35) Protection Level. Change the title of paragraph 2.1.1.13.1 of RTCA/DO-229B to be "Protection Levels" instead of "Protection Level". In lieu of the requirements in paragraph

2.1.1.13.1 of RTCA/DO-229B, substitute the following requirements:

"Class Beta equipment shall output the Horizontal Protection Level (HPLFD as described in Sections 2.1.2.2.2 and 2.1.3.2.2). The equipment shall indicate if the HPLFD cannot be calculated (insufficient number of GPS HEALTHY satellites or inadequate geometry such that fault detection is not available).

"Notes:

1) In addition to the HPLFD, the equipment may output the HUL. The prime item specification may make the HUL output mandatory.

2) When no HPLFD can be calculated, integrity monitoring is not provided.

"To support potential future applications external to the equipment, Class Beta equipment shall also output the Vertical Protection Level (VPLFD). The VPLFD is the vertical analog of the horizontal HPLFD described in Sections 2.1.2.2.2 and 2.1.3.2.2. The VPLFD shall be based on the same missed alert probability, false alert probability, and failed exclusion probability requirements as the HPLFD (see Sections 2.1.2.2.2 and 2.1.3.2.2). The equipment shall indicate if the VPLFD cannot be calculated (insufficient number of GPS HEALTHY satellites or inadequate geometry such that fault detection is not available).

"Notes:

1) In addition to the VPLFD, the equipment may output the VUL. The prime item specification may make the VUL output mandatory.

2) Even if no VPLFD can be calculated, integrity monitoring is still provided by Class

Beta-1 or Class Beta-2 equipment so long as a valid HPLFD value is calculated and output."

(36) Accuracy. In lieu of the requirements in paragraph 2.1.2.1 of RTCA/DO-229B, substitute the following requirements:

“In the keyed PPS mode with SA in effect at any level, under the minimum signal conditions defined in Section 2.1.1.10 and interference conditions defined in Appendix C, the horizontal radial position fixing accuracy for en route (domestic and oceanic) and terminal area navigation shall not exceed 19.6 m, 2drms, when HDOP is normalized to 1.5.

“Notes:

1) The assumptions are as follows: signal-in-space pseudorange accuracy of 6.0 m, 1 sigma and avionics pseudorange accuracy no worse than 2.6 m, 1 sigma (due to receiver noise at minimum signal level, multipath, etc), for a total (root-sum-square) pseudorange accuracy of 6.5 m, 1 sigma. The receiver noise accuracy at minimum signal level is assumed to be no worse than 0.40 m, 1 sigma. The multipath accuracy is assumed to be no worse than 0.70 m, 1 sigma. The dual-frequency ionospheric delay compensation (as a function of pseudorange measurements corrupted by receiver noise and multipath) accuracy is assumed to be no worse than 1.20 m, 1 sigma. The tropospheric delay compensation model accuracy is assumed to be no worse than 2.00 m, 1 sigma. The dynamic propagation and related accuracy is assumed to be no worse than 0.50 m, 1 sigma. Inaccuracies due to flight technical error (FTE), waypoint error, and RNAV path computation error are not included. The 2drms accuracy is approximately equal to the 95th percentile accuracy (98.2% - 95.4%).

2) Section 2.5.8 describes the test for this requirement. In order to reduce the duration of testing required to demonstrate accuracy in the presence of the interference conditions, Section 2.5.8 excludes the accuracy effects of the signal-in-space pseudorange error, the multipath error, the tropospheric delay compensation model error, and the dynamic propagation and related error, and uses a dual-frequency sensor pseudorange accuracy threshold of 0.72 meters and a single-frequency sensor pseudorange accuracy threshold of 0.40 meters.

“In the keyed PPS mode with SA in effect at any level, under the maximum signal the horizontal radial position fixing accuracy for en route (domestic and oceanic) and terminal area navigation shall not exceed 19.4 m, 2drms, when HDOP is normalized to 1.5.

“Notes:

1) The assumptions are as follows: signal-in-space pseudorange accuracy of 6.0 m, 1 sigma and avionics pseudorange accuracy no worse than 2.4 m, 1 sigma (due to receiver noise at maximum signal level, multipath, etc), for a total (root-sum-square) pseudorange accuracy of 6.5 m, 1 sigma. The receiver noise accuracy at maximum signal level is assumed to be no worse than 0.15 m, 1 sigma. The multipath accuracy is assumed to be no worse than 0.70 m, 1 sigma. The dual-frequency ionospheric delay compensation (as a function of pseudorange measurements corrupted by receiver noise and multipath) accuracy is assumed to be no worse than 1.07 m, 1 sigma. The tropospheric delay compensation model accuracy is assumed to be no worse than 2.00 m, 1 sigma. The dynamic propagation and related accuracy is assumed to be no worse than 0.50 m, 1 sigma. Inaccuracies due to flight technical error (FTE), waypoint error, and interference conditions, Section 2.5.8 excludes the accuracy effects of the signal-in-space pseudorange error, the multipath error, the tropospheric delay compensation model error, and the dynamic propagation and related error, and uses a dual-frequency sensor pseudorange accuracy threshold of 0.27 meters and a single-frequency sensor pseudorange accuracy threshold of 0.15 meters.

“In the PPS-LO mode and in the unkeyed PPS mode with SA in effect at the level described in Appendix B, under the minimum signal conditions defined in Section

2.1.1.10 and interference conditions defined in Appendix C, the horizontal radial position fixing error for en route (domestic and oceanic) and terminal area navigation shall not exceed 100 m, 2drms, when HDOP is normalized to 1.5.

“Notes:

1) The assumptions are as follows: signal-in-space pseudorange accuracy of 33 m, 1 sigma (due primarily to SA) and avionics pseudorange accuracy of no more than 5 m, 1 sigma (due to receiver noise at minimum signal level, multipath, etc), for a total (root-sum-square) pseudorange accuracy of 33.3 m, 1 sigma.

Inaccuracies due to flight technical error (FTE), waypoint error, and RNAV path computation error are not included. The 2drms accuracy is approximately equal to the 95th percentile accuracy (98.2% - 95.4%).

interference conditions, Section 2.5.8 excludes the accuracy effects of the signal-in-space pseudorange error (SA and single-frequency ionospheric delay compensation model), the multipath error, the tropospheric delay compensation model error, and the dynamic propagation and related error, and uses a sensor pseudorange accuracy threshold of 5 meters.

“If a time output is provided, it shall be within 1 second of coordinated universal time (UTC) regardless of operating mode.”

(37) FDE-Provided Integrity Monitoring. Replace the requirement relating to the URA and the associated note in paragraph 2.1.2.2.2.2 of RTCA/DO-229B as follows.

Delete the existing text which reads:

"The FDE algorithm shall use the URA broadcast to modify the thresholds for alerting. At a minimum, the FDE algorithm shall set two different thresholds: 1) an SA mode, if any satellite URA's are greater than 16 meters; 2) an SA off mode, if the URA for every satellite being used is less than or equal to 16 meters.

"Note The URA index in the GPS SPS Signal Specification, paragraph 2.5.3 can be used to determine range-domain uncertainty by assuming the URA maps onto the near- Gaussian distribution shown in GPS SPS Signal Specification, Annex B, section 5.2.3."

"The FDE algorithm shall use the broadcast URA information (PPS or SPS, as appropriate) to modify the thresholds used for detection and alerting. The FDE algorithm shall also use estimates of the propagation path delay compensation uncertainties, multipath uncertainties, and pseudorange measurement uncertainties to modify the thresholds used for detection and alerting.

"Note The URA index (Ref. IS-GPS-200) can be used to determine range-domain uncertainty for the signal-in-space, not including any propagation path delay compensation uncertainties, by assuming the URA maps onto a near-Gaussian distribution with a 1-sigma value in meters defined by the relationship given in IS-

GPS-200."

(38) FDE-Provided Integrity Monitoring. Replace the requirement relating to the utilization of barometric altitude in paragraph 2.1.2.2.2.2 of RTCA/DO-229B as follows.

Delete the existing text which reads:

"Equipment which utilizes barometric altitude to improve the performance of this algorithm shall meet the requirements specified in Appendix G."

"When the barometric altitude information is provided by the aircraft to the GPS/PPS equipment, the GPS/PPS equipment shall utilize that information to improve the performance of the FDE algorithm in compliance with the requirements specified in Appendix G. The GPS/PPS equipment shall meet the requirements specified herein regardless of whether barometric altitude information is provided by the aircraft or not."

(39) FDE-Provided Integrity Monitoring. Replace the note relating to the rationale for requiring the FDE capability in paragraph 2.1.2.2.2.2 of RTCA/DO-229B as follows.

Delete the existing text which reads:

"Note: This FDE capability is required in order to provide a transition to primary means navigation utilizing the WAAS. It enables operation outside of the WAAS coverage area and provides a secondary means of providing integrity should a catastrophic WAAS failure occur."

"Note: This FDE capability is required in order to provide primary means of navigation without relying on foreign or domestically operated SBAS services. It enables PPS operation regardless of SBAS coverage areas and provides global en route through non-precision approach access in support of worldwide missions where use of PPS is approved by the host nation."

(40) False Alert Probability. In lieu of the requirements in paragraph 2.1.2.2.2.2.3 of

"The probability of false alert shall be less than or equal to 1x10-5/flight hour in the keyed PPS mode regardless of SA. The probability of false alert shall be less than or equal to 1x10-5/flight hour in the PPS-LO mode or in the unkeyed PPS mode assuming that SA is operating as described in Appendix B. If these requirements are not met for a given geometry, then the detection function is defined to be unavailable for that geometry in that mode (See Section 1.7.3).

"Notes:

1) The testing paragraph defines specific constellations to be used to evaluate this requirement.

2) Without SA effects, the correlation time of PPS pseudorange errors can be assumed to be 6.67 hours (See GPS PPS Performance Standard, Edition 1). If the PPS pseudorange errors correlation time were instead assumed to be 1 hour, the probability of false alert would have been 6.67x10-5/flight hour. With SA effects, the correlation time of SPS pseudorange errors can be assumed to be 2 minutes."

(41) Availability. In lieu of the requirements in paragraph 2.1.2.2.2.2.5 of RTCA/DO-

"The availability of the FDE algorithm to meet the above requirements with an HAL of 1 NM, when evaluated over the constellations and grids specified in the test procedures for Case 0 of Section 2.5.9 (i.e., keyed PPS mode, and SA operating as described in Appendix B), using the same satellite selection algorithm used by the equipment and a physically imposed mask angle of 2 degrees shall be greater than or equal to the following:

Availability of detection: 99.999% Availability of exclusion: 99.900%

"The availability of the FDE algorithm to meet the above requirements with an HAL of 1 NM, when evaluated over the constellations and grids specified in the test procedures for Case 1 of Section 2.5.9 (i.e., in the PPS-LO mode or unkeyed PPS mode, and SA operating as described in Appendix B), using the same satellite selection algorithm used by the equipment and a physically imposed mask angle of 5 degrees shall be greater than or equal to the following:

Availability of detection: 99.800% Availability of exclusion: 94.550%

"The availability of the FDE algorithm to meet the above requirements with an HAL of 1 NM, when evaluated over the constellations and grids specified in the test procedures for Case 2 of Section 2.5.9 (i.e., in the PPS-LO mode or unkeyed PPS mode, and SA set to zero), using the same satellite selection algorithm used by the equipment and a physically imposed mask angle of 5 degrees shall be greater than or equal to the following:

Availability of detection: 99.900% Availability of exclusion: 98.000%

"Note: These requirements are intended to provide a means to assess the adequacy of FDE algorithms. These numbers are based on simulation and analysis of the practical availability and are intended to ensure a consistent minimum capability that can be used by airspace planners and by aircraft operation directors. These availabilities have not been determined to meet all civil operational requirements."

(42) Satellite Tracking Capability. Delete the last sentence of the requirements in paragraph 2.1.2.4 of RTCA/DO-229B, and retain the first sentence, such that the requirement in paragraph 2.1.2.4 shall be as follows:

"The GPS/PPS equipment shall be capable of simultaneously tracking a minimum of 8 GPS satellites."

(43) Accuracy. In lieu of the requirements in paragraph 2.1.3.1 of RTCA/DO-229B, “In the keyed PPS mode with SA in effect at any level, under the minimum signal conditions defined in Section 2.1.1.10 and interference conditions defined in Appendix C.

the horizontal radial position fixing accuracy for non-precision approach navigation shall not exceed 19.6 m, 2drms, when HDOP is normalized to 1.5.

“Notes:

1) The assumptions are as follows: signal-in-space pseudorange accuracy of 6.0 m, 1 sigma and avionics pseudorange accuracy of no more than 2.6 m, 1 sigma (due to receiver noise at minimum signal level, multipath, etc), for a total (root-sum-square) pseudorange accuracy of 6.5 m, 1 sigma. The receiver noise accuracy at minimum signal level is assumed to be no worse than 0.4 m, 1 sigma. The multipath accuracy is assumed to be no worse than 0.7 m, 1 sigma. The dual-frequency ionospheric delay compensation (as a function of pseudorange measurements corrupted by receiver noise and multipath) accuracy is assumed to be no worse than 1.2 m, 1 sigma. The tropospheric delay compensation model accuracy is assumed to be no worse than 2.0 m, 1 sigma. The dynamic propagation and related accuracy is assumed to be no worse than 0.5 m, 1 sigma.

Inaccuracies due to flight technical error (FTE), waypoint error, and RNAV path interference conditions, Section 2.5.8 excludes the accuracy effects of the signal-in-space pseudorange error, the multipath error, the tropospheric delay compensation model error, and the dynamic propagation and related error, and uses a dual-frequency sensor pseudorange accuracy threshold of 0.72 meters.

“In the keyed PPS mode with SA in effect at any level, under the maximum signal the horizontal radial position fixing accuracy for non-precision approach navigation shall not exceed 19.4 m, 2drms, when HDOP is normalized to 1.5.

“Notes:

1) The assumptions are as follows: signal-in-space pseudorange accuracy of 6.0 m, 1 sigma and avionics pseudorange accuracy no worse than 2.4 m, 1 sigma (due to receiver noise at maximum signal level, multipath, etc), for a total (root-sum-square) pseudorange accuracy of 6.5 m, 1 sigma. The receiver noise accuracy at maximum signal level is assumed to be no worse than 0.15 m, 1 sigma. The multipath accuracy is assumed to be no worse than 0.70 m, 1 sigma. The dual-frequency ionospheric delay compensation (as a function of pseudorange measurements corrupted by receiver noise and multipath) accuracy is assumed to be no worse than 1.07 m, 1 sigma. The tropospheric delay compensation model accuracy is assumed to be no worse than 2.00 m, 1 sigma. The dynamic propagation and related accuracy is assumed to be no worse than 0.50 m, 1 sigma. Inaccuracies due to flight technical error (FTE), waypoint error, and interference conditions, Section 2.5.8 excludes the accuracy effects of the signal-in-space pseudorange error, the multipath error, the tropospheric delay compensation model error, and the dynamic propagation and related error, and uses a dual-frequency sensor pseudorange accuracy threshold of 0.27 meters and a single-frequency sensor pseudorange accuracy threshold of 0.15 meters.

“In the PPS-LO mode and in the unkeyed PPS mode with SA in effect at the level described in Appendix B, under the minimum signal conditions defined in Section

2.1.1.10 and interference conditions defined in Appendix C, the horizontal radial position fixing error for non-precision approach navigation shall not exceed 100 m, 2drms, when HDOP is normalized to 1.5.

“Notes:

1) The assumptions are as follows: signal-in-space pseudorange accuracy of 33 m, 1 sigma (due primarily to SA) and avionics pseudorange accuracy of no more than 5 m, 1 sigma (due to receiver noise at minimum signal level, multipath, etc), for a total (root-sum-square) pseudorange accuracy of 33.3 m, 1 sigma.

Inaccuracies due to flight technical error (FTE), waypoint error, and RNAV path interference conditions, Section 2.5.8 excludes the accuracy effects of the signal-in-space pseudorange error (SA and single-frequency ionospheric delay compensation model), the multipath error, the tropospheric delay compensation model error, and the dynamic propagation and related error, and uses a sensor pseudorange accuracy threshold of 5 meters.

“If a time output is provided, it shall be within 1 second of coordinated universal time (UTC) regardless of operating mode.”

(44) Availability. In lieu of the requirements in paragraph 2.1.3.2.2.2.5 of RTCA/DO-

"The availability of the FDE algorithm to meet the above requirements with an HAL of 0.3 NM, when evaluated over the constellations and grids specified in the test procedures for Case 0 of Section 2.5.9 (i.e., keyed PPS mode, and SA operating as described in Appendix B), using the same satellite selection algorithm used by the equipment and a physically imposed mask angle of 2 degrees shall be greater than or equal to the following:

Availability of detection: 99.990% Availability of exclusion: 99.400%

"The availability of the FDE algorithm to meet the above requirements with an HAL of 0.3 NM, when evaluated over the constellations and grids specified in the test procedures for Case 1 of Section 2.5.9 (i.e., in the PPS-LO mode or unkeyed PPS mode, and SA operating as described in Appendix B), using the same satellite selection algorithm used by the equipment and a physically imposed mask angle of 5 degrees shall be greater than or equal to the following:

Availability of detection: 97.060% Availability of exclusion: 57.300%

"The availability of the FDE algorithm to meet the above requirements with an HAL of 0.3 NM, when evaluated over the constellations and grids specified in the test procedures for Case 2 of Section 2.5.9 (i.e., in the PPS-LO mode or unkeyed PPS mode, and SA set to zero), using the same satellite selection algorithm used by the equipment and a physically imposed mask angle of 5 degrees shall be greater than or equal to the following:

Availability of detection: 99.700% Availability of exclusion: 92.000%

"Note: These requirements are intended to provide a means to assess the adequacy of FDE algorithms. These numbers are based on simulation and analysis of the practical availability and are intended to ensure a consistent minimum capability that can be used by airspace planners and by aircraft operation directors. These availabilities have not been determined to meet all civil operational requirements."

(45) Airborne Equipment Performance - Environmental Conditions.