Attachment 7 FAA-E-2716 Mode S Specification.pdf

DEPARTMENT OF TRANSPORTATION

FEDERAL AVIATION ADMINISTRATION

SPECIFICATION MODE SELECT

BEACON SYSTEM SENSOR

1.0 SCOPE

1.1 Scope.- This specification contains the requirements for the design, fabrication, quality assurance, and preparation for delivery of a Mode Select (Mode S) Beacon System Sensor. This sensor singly and in cooperation with other sensors, will provide surveillance of ATCRBS- and Mode S-equipped aircraft and two-way digital communications with aircraft equipped with Mode S transponders.

Surveillance data and data-link services will be provided via suitable land links to the NAS Terminal and En Route control and display facilities, and to flight services automation systems.

1.2 Classification.- Three types of Mode S sensors of varying capacity and configuration are covered by this specification.

1.2.1 Type.- Mode S sensors differing in these basic characteristics are covered by this specification:

Type I - Terminal sensor.- This type includes provisions for interfacing with an airport surveillance radar (ASR) antenna having a single face, a five channel (3 beacon, 2 radar) rotary joint, and an RF feed suitable for beacon interrogation and reception. Software for this type of Mode S sensor is capable of managing beacon interrogations and replies from a single antenna face.

Type IIA - Single face en route sensor.- This type includes provisions for interfacing with air route surveillance radar (ARSR) antenna having a single face, a rotary joint with 3 beacon plus radar channels, and an RF feed suitable for beacon interrogation and reception. Software for this type of Mode S sensor is capable of managing beacon interrogations and replies from a single antenna face.

Type IIB - Back-to-back en route sensor.- This type includes provisions for interfacing with an air route surveillance radar (ARSR) antenna having back-to-back beacon antenna faces (requiring 6 beacon plus radar channels in the rotary joint), and computer subsystem controlled switching between two oppositely pointing beacon antenna faces. Software for this type of Mode S is capable of handling beacon interrogations and replies from the two back-to-back beacon antenna faces.

Type IIIA - Single face en route joint use sensor.- This type includes provisions for interfacing with an air route surveillance radar antenna having a single face beacon antenna (requiring 3 beacon plus radar channels) shared by the FAA and the Air Defense Command (ACCOM).

Software for this sensor type is capable of handling beacon interrogations and replies from a single antenna face.

Type IIIB - Back-to-back en route joint use sensor.- This type includes provisions for interfacing with an air route surveillance radar antenna having back-to-back beacon antenna faces shared by the FAA and the Air Defense Command (ADCOM). Further, this sensor type is capable of transmitting Mode 4 interrogations from its front face while Mode S interrogations are being transmitted from the rear face (requiring 6 beacon plus radar channels in the rotary joint).

Software for this sensor type is capable of handling beacon interrogations and replies from the oppositely pointing antenna faces, and switching between mode types upon command.

1.2.2 Capacity.- The traffic handling capacity of a Mode S sensor of any type shall be denoted Class I, Class II, or Class III as specified in 3.3.2.5. The sensor class shall be as specified in the contract schedule.

1.2.3 Auxiliary equipment.- A Mode S sensor shall be able to operate in conjunction with auxiliary equipment as listed below. Requirements for each equipment and its Interface with the Mode S sensor are specified in appendices and subsections of this specification. The number of each of these equipment items to be furnished shall be as specified in the contract schedule:

Auxiliary Equipment Requirement

(a) Performance monitor display 3.4.10.4

(b) Programming or Mode S support facility Appendix II

(c) Back-to-back antenna Appendix III

(d) Terminal radar systems Appendix IV

(e) Joint-use sites Appendix V

(f) Video reconstitutor and surveillance data selector Appendix VI

(g) Beacon decoder Appendix VI-A

(h) Video delay unit Appendix VII

(i) Calibration and performance monitor equipment Appendix VIII

(j) Aircraft reply and interference environment simulator Appendix IX

2.0 APPLICABLE DOCUMENTS

2.1 Applicable documents.- The following specifications and standards, of the Issues specified in the request for proposal, form a part of this specification. This specification shall have precedence over all specifications, standards, documents, etc., listed or referenced herein, in the event of conflict.

2.2 FAA documents.-

2.2.1 FAA standards.-

FAA-STD-002 Engineering Drawings FAA-STD-005 Preparation of Specifications

FAA-STD-007

Program Evaluation Review Technique (PERT) Procedures for Contract Use

FAA-STD-010 Graphic Symbols for Digital Logic Equipment FAA-STD-016 Quality Control System Requirements FAA-STD-018 Software Quality Assurance Standards

FAA-STD-019

Lightning Protection, Grounding, Bonding and Shielding Requirements for Facilities

FAA-STD-020

Transient Protection, Grounding, Bonding and Shielding Requirements for Equipment

FAA-STD-021 Configuration Management

2.2.2 FAA specifications.-

FAA-C-1217 Electrical Work, Interior

FAA-D-2494

Technical Instruction Book Manuscript: Electronic, Electrical, and Mechanical Equipment, Requirements for Preparation of Manuscript and Production of Books

FAA-E-2217 Digital Data Communications System FAA-E-2660 ATCRBS Open Array Antenna (5 ft.)

FAA-E-2679 Common Digitizer-2 (CD-2) FAA-E-2698 Maintenance Processor Subsystem FAA-E-2704 Airport Surveillance Radar (ASR-9), Appendix III, MTD/Mode S Interface FAA-G-1210 Provisioning Technical Documentation FAA-G-1375 Spare Parts-Peculiar for Electronic, Electrical, and

Mechanical Equipment FAA-G-2100 Electronic Equipment, General Requirements FAA-ER-240-35a Antenna Group, Enroute DABS/ATCRBS, Array FAA-ER-240-35b Antenna Group, Enroute Beacon, Array

2.2.3 Other FAA documents.-

FAA-RD-76-219 DABS Monopulse Summary

FAA-RD-78-96 The Aircraft Reply and Interference Environment Simulator

(ARIES)

FAA-RD-80-14 DABS/ATC Facility Surveillance and Communication Message Formats Note: This document will be replaced by a series of Interface Control Documents (ICDs) in preparation. See section 2.4.

FAA-RD-80-37 DABS Front End Processor/Enroute Central Computer Complex Protocol

FAA-RD-80-38 ATC Facility Hardware Interfaces for Mode S FAA-RD-81-39 A Los Angeles Basin 1100 Aircraft Traffic Model, January

DOT/FAA-RD-82/37 Generation of the Mode Select Sensor Coverage Map DOT/FAA-RD-82/52 Mode S Functional Description DOT/FAA-RD-82/58 Mode S Installation and Siting Criteria FAA Order 1010.51A U.S. National Standard for the IFF Mark X (SIF) Air Traffic

Control Radar Beacon System (ATCRBS) Characteristics FAA Order 1320.33 Equipment Modification and Facility Instruction Directives FAA Order 1800.8 National Airspace System Configuration Management FAA Order AF 6000.1 Airways Facilities Service Maintenance Program FAA Order 6032.1 Modification to Ground Facilities, Systems, and Equipment in the National Airspace System FAA Order 6365.1A U.S. National Standard for the Mode Select Beacon System FAA Order 6950.19 Practices and Procedures for Lightning Protection, Grounding, Bonding and Shielding Implementation NAS-MD-311 Computer Program Functional Specification, Message Entry and Checking NAS-MD-636A Remote SRAP Processing NAS-MD-790 Interface Control Document for The Remote Maintenance

Monitoring System (RMMS) (Level I ICD) NAS-MD-791 Guidelines for the Development of Level II Interface Control

Documents for Remote Maintenance Monitoring System

(RMMS)

NAS-MD-792 Operational Requirements for the Remote Maintenance Monitoring System (RMMS)

TI 6350.7 FAA Technical Manual, Transmitting Set, Coordinate Data, Models AN/FYQ-47, AN/FYQ-49, AN/FYQ-56, Service Instructions

TI 6350.8 FAA Technical Manual, Transmitting Set, Coordinate Data, Models AN/FYQ-47, AN/FYQ-49, AN/FYQ-56, Circuit Diagrams

TI 6350.11 FAA Technical Manual, AN/FYQ-47 and AN/FYQ-49 Assemblies Tested on Test Set, Electronics Circuit Plug-in Unit, Model AN/FYQ-27 — Service Instructions, Circuit Diagrams, and Illustrated Parts Breakdown

FAA Drawing No D-6048-1 ASR-4,-5,-6 Prefabricated Metal Building Typical Site Construction

2.3 Other documents.-

MIL-HDBK-217 Reliability Prediction of Electronic Equipment MIL-STD-275 Printed Wiring for Electronic Equipment MIL-STD-280 Definitions of Item Levels, Item Exchangeability, Models, and Related Terms MIL-STD-454 Standard General Requirements for Electronic Equipment MIL-STD-461 Electromagnetic Interference Characteristics Requirements for Equipment MIL-STD-470 Maintainability Program Requirements for Systems and

Equipment MIL-STD-471 Maintainability Verification Demonstration and Evaluation MIL-STD-756 Reliability Prediction MIL-STD-781 Reliability Tests, Exponential Distribution MIL-STD-785 Reliability Programs for Systems and Equipment

Development and Production MIL-STD-965 Parts Control Program MIL-STD-1130 Connectors, Electrical, Solderless MIL-E-75 Electron Tubes, Preparation for Delivery of MIL-E-17555 Electronic and Electrical Equipment Accessories and Repair

Parts, Packaging and Packing of

ANSI X3.28-1976

ANSI X3.66-1979 National Standard for Advanced Data Communication

Control Procedures (ADCCP) TO 31P4-2GPA124-2 Coder-Decoder Group, AN/GPA-124 EIA-RS-422-A Electrical Characteristics of Balance Voltage Digital

Interface Circuits EIA-RS-449 General Purpose 37-Position and 9-Position Interface for

Data Terminal Equipment and Data Circuit - Terminating

Equipment Employing Serial Binary Data Interchange, November 1977.

FIPS PUB 3 Recorded Magnetic Tape for Information Exchange (800

CPI, NRZI)

FIPS PUB 17-1

FIPS PUB 25 Recorded Magnetic Tape for Information Exchange (1600

CPI, phase encoded) FIPS PUB 38 Guidelines for Documentation of Computer Programs and

Automated Data Systems.

IEEE 488 (1975) IEEE Standard Digital Interfaces for Programmable

Instrumentation NFPA-70 National Electrical Code NFPA-78 Lightning Protection, Code, ANSI C5.1

2.4 Interface Control Documents.-

Mode S/ASR-9/SCIP to ARTS Mode S/ASR-7/8/SCIP to ARTS Mode S to ASR-9 Mode S to CD-2 Mode S to ARSR-3 Mode S to JSS Mode S to SRAP Mode S to Remote Maintenance Monitoring System (RMMS)

2.5 Availability of documents.- Copies of this specification and other applicable FAA specifications, standards and drawings may be obtained from the Contracting Officer in the Federal Aviation Administration Office issuing the invitation for bids or request for proposals. Requests should fully identify material desired, i.e., specification, standard, amendment, and drawing numbers and dates.

Requests should cite the invitation for bids, request for proposals, or the contract involved or other use to be made of the requested material.

Single copies of Military specifications and standards may be obtained from Federal Aviation Administration, Washington, DC 20591, ATTN: Contracting Officer. Requests should cite the invitation for bids, request for proposals, or contract for which the material is needed. Mail requests, if found acceptable, will be forwarded to a Military supply depot for filling; hence, ample time should be allowed.

Copies of the Federal Information Processing Standards Publications are for sale by the Superintendent of Documents, microsecond Government Printing Office, Washington, DC 20442.

Copies of the National Electrical code may be obtained from the National Fire Protection Association, 470 Atlantic Avenue, Boston, MA 02210

3.0 REQUIREMENTS

This specification covers a set of equipment including hardware and software which when taken together constitute a Mode S sensor. In addition to supplying the sensor hardware and software, the contractor shall, as specified herein provide appropriate documentation for the sensor;

Software provided in response to this requirement shall be modular and flexible. Changes to sensor algorithms shall be possible without severe impact on the remainder of the sensor software.

Validity checking or error correction and detection procedures shall be as specified herein. In addition, the contractor shall incorporate such other validity checking procedures in the computer programs which are in accordance with good programming practice.

3.1 Equipment and services to be furnished.-

3.1.1 Contractor furnished.- The contractor shall provide all necessary manpower, services, and materials to design, fabricate, assemble, test, deliver and install the sensor hardware and associated software as specified herein. Also, the contractor shall interconnect, test, and demonstrate the ability of the system, the subsystems, and all other equipment furnished, to meet specified performance requirements. Any feature or item necessary for proper operation of the system as specified herein, shall be incorporated even though that item may not be specifically described herein. The Mode S sensor shall be provided in the quantities and at the times specified by the contract. Where required by the contract, the work to be performed shall include any modifications and checkout of existing Government Furnished Equipment (GFE) as a part of the overall contractor system checkout effort. In addition, the contractor shall provide all necessary services and material to prepare, reproduce and provide reports, computer programs and documentation as specified herein.

All equipment and services shall be delivered to the locations specified by the Government. All facilities, parts and hardware, including system/subsystem grounding plates, receptacles, connectors, cabling wiring, adapters, and outlets, except GFE specified in 3.1.2, shall be provided to enable the components of each system to be assembled and interconnected as required by this specification. The major items of equipment and services to be furnished are:

(a) A dual channel Mode S sensor - Each channel shall consist of an interrogation subsystem, a computer subsystem, and all necessary communications and interfaces between parts of the Mode S sensor, and between the Mode S sensor and external facilities and equipment as specified herein and called out in the contract.

(b) Any simulators, monitoring, checkout, and calibration equipment which may be specified herein and called out in the contract.

(c) Programming support facilities as specified herein and called out in the contract.

(d) Functional and support software.

(e) A module and system quality assurance program for both hardware and software (4.0).

(f) A system reliability and maintainability program (3.9).

(g) Documentation as specified in 3.13.

(h) Special tools and test equipment.

(i) Spare parts, subassemblies and/or units as mutually agreed to between the contractor and the

Government.

(j) Modifications to azimuth pulse generators, as required in the contract schedule.

3.1.2 Government furnished.- The Government will provide and/or install the following hardware and services:

(a) Data required by the contractor for each site to develop appropriate system and site adaptation parameters, and to prepare coverage map information in the form required by the sensor.

(b) All modems, communication lines, and/or networks required by the Mode S sensor for communication with external facilities and other Mode S sensors.

(c) ATC computer hardware and software in accordance with the ICDs.

(d) Any special simulators, monitoring, test equipment, test tapes, and test aircraft scenarios not supplied by the contractor (3.1.1(b)) which are deemed necessary for successful completion of the project and proper operation of the sensor as mutually agreed to between the contractor and the Government.

3.2 Not Used.-

3.3 Sensor requirements.-

3.3.1 ATC system compatibility.- The Mode S sensor is the basic ground element of the Mode S surveillance and communication system. It must be compatible with other elements of Mode S (e.g., antennas and transponders) and with elements of the overall ATC system (e.g., Mode S Terminal and En Route). To ensure this compatibility, interfaces to these and other equipments shall utilize the signal and message formats specified in the Mode S National Standard and in the appropriate Mode S interface control document (ICD).

3.3.2 Performance requirements.-

3.3.2.1 Surveillance.- The Mode S sensor shall perform surveillance of all beacon-equipped aircraft within its volume of coverage. Nominal maximum operational range shall be 255 nmi, site adaptable to appropriate shorter ranges. ATCRBS-equipped aircraft shall be interrogated by means of the ATCRBS/Mode S All-Call, ATCRBS-Only or ATCRBS interrogation at a rate that produces a fixed number of interrogations in a 3 dB beamwidth. This number shall be adjustable during site adaptation, from a nominal value of 4 to a maximum number of 6, except that the maximum interrogation rate shall not exceed 150 interrogations per second. Mode S-equipped aircraft shall be acquired by means of an ATCRBS/Mode S All-Call interrogation, a Mode S Only All-Call interrogation, or by means of ground-to-ground handover. After acquisition, Mode S-equipped aircraft shall be interrogated with a unique address call. For both ATCRBS and Mode S, azimuth shall be determined by a monopulse technique. When the Mode S sensor is collocated with a primary radar, the Mode S sensor shall accept the digitized radar target declarations and correlate them with beacon (ATCRBS and Mode S ) data, prior to sending the surveillance data, to NAS Terminal and En Route. In addition, Mode S shall perform radar only scan-to-scan surveillance processing when interfaced to a Moving Target Detector (MTD) or Sensor Receiver and Processor (SRAF) (see Appendices).

3.3.2.2 Data link.- The Mode S sensor shall also provide a two-way digital data link for all Mode S-equipped aircraft. Messages originating on the ground, from NAS Terminal, En Route and non-ATC sources, shall be sent to the aircraft, and appropriate acknowledgment received and relayed to the sender. The Mode S sensor shall also manage the data link so that any time an aircraft wishes to initiate an air-to-ground message, that message will be read out with minimum delay. All message types are specified in the Mode S National Standard.

3.3.2.3 Continuity.- In performing its basic surveillance and communication functions the Mode S sensor shall participate with adjacent sensors to provide a continuity of service as aircraft move from one coverage area to another. Continuity of service shall also be provided by the network of sensors in the event of certain prescribed failures, up to the limit of the combined field-of-view of the sensors remaining active after a failure.

3.3.2.4 Not Used.-

3.3.2.5 Capacity.- Each Class I sensor shall be designed to handle (to provide surveillance of all aircraft and data link services to Mode S aircraft) a total of 250 aircraft, each Class II sensor to handle a total of 400 aircraft, and each Class III sensor to handle a total 700 aircraft. Each aircraft population (250, 400, 700) shall be understood to contain any mix of Mode S, ATCRBS, and primary radar targets. Each sensor shall also handle the additional non-aircraft target reports as received from a primary radar interface (3.5.2). The design shall be capable of being altered simply (by the addition or removal of computer hardware and software modules) in order to accommodate 250, 400, or 700 aircraft. The capacity requirements stated shall be achieved when six ATCRBS/All-Call intervals are provided within the ∆/Σ = -2 to +2 antenna beamwidth (equivalent to four intervals within 3 dB antenna beamwidth), and the sensor antenna is rotating at a maximum of 12.5 RPM. Target overload conditions shall be handled in an orderly manner (e.g., reduction of range within which targets are processed).

3.3.2.5.1 Target bunching.- The targets will not necessarily be distributed uniformly in azimuth or range. Some areas of airspace may contain more targets than other areas. The sensors shall be designed to handle any mix of targets in the cases of azimuthal bunching shown below when subjected to the fruit environment stated in 4.3.3.5.2.5:

Case I:

90° Quadrant Bunching - 250 targets within a 90° quadrant 11.25° Sector Bunching - 50 targets within each 11.25° sector for up to four consecutive sectors 2.4° Wedge Bunching - 12 targets within a 2.4° wedge for up to two consecutive wedges

Case II:

90° Quadrant Bunching - 250 targets within a 90° quadrant 11.25° Sector Bunching - 50 targets within each 11.25° sector for up to four consecutive sectors 2.4° Wedge Bunching - 32 targets within a 2.4° wedge

These requirements shall be met simultaneously (all target bunching within one scan) for a uniform range distribution of targets within 50 nmi from the sensor using the nominal antenna beamwidth of

2.4 degrees and a nominal scan rate of 12.5 RPM. The ATCRBS listening window to be used in demonstrating this requirement shall be not less than 2 ms. The above bunching may occur consecutively (limited to sensor capacity) and simultaneously (e.g., peak wedge within a peak sector).

3.3.2.5.2 Data link peaking.- Each sensor shall be designed to provide full data channel utilization (ground-air-ground) under any data link scenario realizable within the channel time-line.

Demonstration of efficient data channel utilization by each sensor shall be accomplished by simultaneously satisfying (within one scan) the following cases of data link peaking for the target distributions specified in 3.3.2.5.1. ‘Interrogation’, as used in the following paragraphs, is defined as an interrogation of an aircraft by the sensor and the inclusion of the corresponding reply window on the channel time-line. An all-Mode S target mix is assumed except where noted. The capacity requirements specified shall be achieved when six ATCRBS/All-Call intervals are provided within the ∆/Σ = -2 to +2 antenna beamwidth (equivalent to four intervals within the 3 dB antenna beamwidth).

These requirements are summarized in Table 3.3.2.5-1.

TABLE 3.3.2.5-1 CAPACITY REQUIREMENTS

(a) Surveillance capacity for each scan (any mix of Mode S and ATCRBS targets):

Sensor Class

Total Surveillance Target Bunching 90° 11.25° 2.4°

I 250 250 50 32

II 400 250 50 32

III 700 250 50 32

(b) Message storage capacity:

Sensor Class

Nominal Uplink Message Storage

Maximum Uplink Message Storage

Downlink Message Storage

I 1800 4800 400

II 2800 4800 600

III 2800 4800 1100

(c) Mode S Data link capacity:

Case I: Each ELM below is a 16-Segment ELM. The final Comm-C/Comm-D transactions for the ELM's, in the 2.4° wedges, are included in the count of Comm-A/ Comm-B transactions specified for the wedges. The 2.4° wedge loading shall occur for two consecutive 2.4° wedges. The 11.25° sector loading shall occur for four consecutive 11.25° sectors. The targets transmitting N Comm-B's include air-initiated Comm-B's as follows: (1); 5 in each of the 2.4° wedges, (2); 8 in each of the 11.25° sectors, (3); 32 in the 90° quadrant. The air-initiated Comm-B's shall be no more than one message per aircraft, uniformly distributed in range over the set of aircraft, specified above, in part (a) of this table.

Type of Peaking (per scan)

Number of Mode S Targets

Targets Receiving N Comm-A' s where N = 1248

Targets Transmitting N Comm-B's Where N = 1 2 3 4

Targets Receiving Uplink ELM's

Targets Transmitting Downlink ELM's

2.4° Wedge 12 4 0 5 3 3 2 1 1 1 0

11.25° Sector 50 24 0 20 6 8 4 2 2 8 3

90° Quadrant 250 140 0 85 25 32 16 8 8 40 15

Case II: Each ELM below is a 16-Segment ELM. The 2.4° wedge loading shall occur once. The 11.25° sector1 sector loading shall occur once and contains the 2.4° wedge when the sector and wedge overlap. The 11.25° sector2 loading shall occur for three consecutive 11.25° sectors and shall be adjacent to the sector1 sector. The targets transmitting N Comm-B's include air-initiated Comm-B's as follows: (1); 5 in the 2.4° wedge, (2); 8 in each of the 11.25° sectors, (3); 32 in the 90° quadrant. The air-initiated Comm-B's shall be no more than one message per aircraft, uniformly distributed in range over the set of aircraft, specified above, in part (a) of this table.

Type Number of of Peaking (per scan)

Targets Receivin g Mode S Targets

Targets 5 N Comm-A's Where N =

1 2 4 8

Targets Transmitting N Comm-B's Where N =

1 2 3 4

Targets Receiving Uplink ELM's

Transmitting Downlink ELM's

2.4° Wedge 32 0 32 0 0 14 0 0 0 0 0

11.25° Sectorl

11.25° Sector2

0 32 10 6

24 0 20 6

18 1 2 1

8 4 2 2

3.

90° Quadrant 250 116 32 75 25 42 13 8 7 40 15

3.3.2.5.2.1 Data link quadrant peaking.- Each sensor shall be able to handle the data link message capacity specified in Table 3.3.2.5-1 for the 90° quadrant peaking. The sensor shall handle this loading each scan. The sensor shall handle all the cases shown in table 3.3.2.5-1.

3.3.2.5.2.2 Data link sector peaking.- Each sensor shall be able to handle the data link message capacity specified in table 3.3.2.5-1 for the 11.25° sector peaking. The sensor shall handle this loading each scan. The sensor shall handle all the cases shown in table 3.3.2.5-1.

3.3.2.5.2.3 Data link wedge peaking.- Each sensor shall be able to handle the data link message capacity specified in table 3.3.2.5-1 for the 2.4° wedge peaking. The sensor shall handle this loading each scan. The sensor shall handle all the cases shown in Table 3.3.2.5-1.

3.3.2.5.3 Data link message storage.- Each sensor shall have a nominal uplink message (Comm-A or Comm-C segment) storage capacity of 1800 messages for the 250 aircraft capacity sensor, and 2800 messages for the 400 and 700 aircraft capacity sensors. This message storage capacity shall be easily expandable to a limit of 4800 messages. In addition, each sensor shall have a downlink message (Comm-B or Comm-D segment) storage capacity of 400 messages for the 250 aircraft capacity sensor, 600 for the 400 aircraft capacity sensor, and 1100 for the 700 aircraft capacity sensor. These requirements are summarized in Table 3.3.2.5-lb.

3.3.2.5.4 Transfer of remote data.- Under any load condition, each sensor shall be capable of providing remote sensor data on 15% of the tracks in the sensor's track file to two adjacent sensors (Complete track file will be transmitted within 7 scans). Under any load condition the sensors shall be able to receive remote sensor data on 15% of the tracks in the sensor's track file from two adjacent sensors (Complete track file will be received within 7 scans).

3.3.2.6 Data delays.- The following data delay requirements are to be met for all capacity conditions specified in 3.3.2.5.

3.3.2.6.1 Surveillance data.- All surveillance data for targets greater than 10 nmi (slant range) from the sensor shall be processed and available for transmission from the sensor to the ATC facilities (both correlating and noncorrelating users) no later than 3/32 of a scan period, nor sooner than 5/64 of a scan period, after their acquisition by the sensor. For targets within 10 nmi (slant range) the additional processing delay required for execution of the correlation rules specified in 3.4.6.4.10 may be added to the 3/32 of a scan period limit previously specified for dissemination of the surveillance data to non-correlating users. Each surveillance report shall be time-tagged so that accurate tracking and timing can be accomplished at the ATC facilities.

3.3.2.6.2 Communication messages.- All uplink messages shall be delayed no more than 1/16 of a scan period from time of receipt until they are processed and available for delivery to the aircraft. All downlink communication messages shall be delayed no more than 1/16 of a scan period from the time the message is received until it is available for transmission from the sensor.

3.3.2.7 General accuracy requirements.- The range and azimuth accuracy requirements specified herein apply to the combined antenna and sensor subsystem. Compliance shall be demonstrated using the general test methods described in section 4.0 of this document using stationary, controlled test transponders, and live aircraft.

Independent software offset adjustments for the mean position error (bias) values for both range and azimuth shall be provided. The mean position error values measured using either Mode S or ATCRBS reports shall be adjustable such that the mean errors for either report type may be nulled to less than one range or azimuth unit. Operationally compatible calibration procedures, employing these capabilities, shall be developed and used as part of the accuracy tests.

Demonstration of the sensor and antenna accuracy requirements shall be accomplished using a government furnished five-foot open array antenna as described in FAA-E-2660 and FAA-ER-240- 35a. The sensor hardware and software parameters which affect accuracy (e.g., ATCRBS PRF) shall be set to the nominal values specified herein for the conduct of these tests.

These accuracy requirements shall be demonstrated using both the Terminal (Type I) and En route (Type II or III) configurations. However, for the back-to-back en route configurations, specification compliance shall be demonstrated separately for each of the antenna faces. The bias difference between the two faces shall be less than one azimuth unit.

3.3.2.8 Accuracy values.- Under the test conditions specified in section 4.0 of this document the following accuracy values shall be demonstrated. These requirements apply for received power levels at least 10 dB greater than Minimum Threshold Level (MTL) as defined in 3.4.3.2.1, and for transponders meeting the characteristics specified in the Mode S National Standard.

3.3.2.8.1 Range accuracy.- The sensor-only range errors, measured using either Mode S or ATCRBS reports, shall not exceed ± 30 feet bias (including long term drift) and 25 feet rms jitter for either Mode S or ATCRBS reports.

3.3.2.8.2 Azimuth accuracy.- The long term combined sensor plus antenna azimuth accuracy, using the government furnished five-foot open array antenna, measured separately for Mode S reports, and for ATCRBS reports, shall not exceed the following values for the indicated antenna elevation angles:

Bias (Elevation angles < 2°): within ± 0.033° (exclusive of antenna wind loading but including long term drift).

Jitter (Elevation angles < 20°): less than 0.060°, lσ; or the equivalent RMS error of 0.068°, lσ.

In addition to the low elevation (< 2°) requirements stated above, the azimuth bias component as measured using Mode S reports only, will be permitted to change as a function of the elevation angle due to the GFE antenna beam widening (The bias component change is defined as the difference between the azimuth bias component measured at elevation angles less than 2° and the bias component values measured at higher elevation angles). The sensor and antenna reported azimuth bias component change shall not exceed the change attributable to the antenna only. The allowable limits will be established by the government from measured antenna-only data. The antenna requirements pertinent to elevation induced errors are defined in FAA-E-2660, paragraph 3.3.1.2.3 and in FAA-ER-240-35a, paragraph 3.3.1.8.

3.3.2.9 RF link reliability.- High RF link reliability both for surveillance and for two-way data link shall be achieved in part by means of two design features. Each sensor shall be capable of reinterrogation within a beam dwell time, such that in case of failure to reach an aircraft on a single call, multiple additional calls can be made before the antenna beam passes by the aircraft. The sensor shall be designed to handle the average reinterrogation rate of 10 percent, which is included in the capacity requirements. In addition, each sensor shall be capable of working in a prescribed manner with adjacent sensors, which have a common coverage volume, to provide multiple surveillance and data-link coverage.

3.3.2.10 Sensor reliability.- The sensor shall be designed for high reliability and minimum maintenance. The design requirement is for preventive maintenance no more frequently than once every 91 days, with incidence of system failure averaging no more than once in 20,000 hours.

3.3.2.11 Detection and false alarm performance.- The sensor shall achieve the following reply probability of detection (PD) and reply probability of false alarm (PFA) performance under the conditions specified:

Mode S ATCRBS CONDITION

PD >= 0.99 >= 0.99 Received reply power >= -76 dBm referenced to the sensor RF port in the absence of signal (RF) interference

PFA <= 10-6 <= 10-6 In any one second interval with no signal (RF) interference.

In addition, the sensor shall demonstrate the overall detection and false alarm performance specified in

4.3.3.5.5 when operating in a controlled, simulated environment.

3.3.3 Interfaces.

3.3.3.1 Antennas.- Each Mode S sensor shall be designed to interface and operate with minimal adjustment with several antennas. The nominal antennas for operational use are specified in 3.5.1 (Each has sum, difference, and omni channels, for monopulse angle determination and sidelobe suppression). Rotation rates from 5 to 15 rpm (inclusive) shall be accommodated. Nominal 3 dB beamwidth shall be 2.4°.

3.3.3.2 Primary radar.- The Mode S sensor shall be capable of accepting digital surveillance data from a collocated (primary) radar for surveillance processing and correlation along with the beacon data.

Collocated means that both primary and beacon antennas use the same pedestal. This data will come from a radar digitizer. The radar target reports, which are made available to the sensor within 3/64 of a scan, measured from the time of reported azimuth, shall be correlated with beacon reports and coasted tracks.

The basic Mode S sensor shall not track primary radar targets. However, if the contract schedule requires that Appendix IV be implemented, the sensor shall perform surveillance processing of primary radar target reports when interfaced to either an MTD or a SRAP/RDAS.

3.3.3.3 NAS facilities.- The principal user interfaces to the Mode S surveillance and data link networks are to computers located in the MAS ATC facilities. The Mode S sensor shall use two types of digital interface to each facility: a two-way communication and an one-way surveillance link from sensor to ATC, the formats and structure required, for these links are described in FAA-RD-80-14. The data rates are specified in 3.5.3.

The sensor shall have up to six surveillance links and six communication links. This capability will serve up to 6 external facilities or systems. ATC data link services will utilize links between the Mode S sensor and ATC facilities. In the initial implementation of Mode S, the only non-ATC data link service will utilize links between, the Mode S sensor and the Weather and Communications Processor (WCP) The number of interfaces to be delivered with each sensor shall be as specified in the contract schedule. The surveillance and communications links shall be compatible with service to the NAS Terminal Automation System, the NAS En Route Automation System, and non-ATC (communications only).

3.3.3.4 Not used.

3.3.3.5 Sensor-to-programming support facility.- The sensor shall have a two way,dial-up,4800 bit/second digital communications link for data transmission between the sensor and the programming support facility (PSF) or sensor support facility (SSF). This communications link will be used for maintenance purposes as described in 3.8.4.

3.3.4 Sensor functions.- Figure 3.3.4-1 is an overall block diagram of the sensor, illustrating the principal functions and showing the interfaces to other systems. This diagram is not binding upon the actual physical arrangement of hardware and software except as specified in 3.7. The sensor functions, as described in this section, include the general requirements for each major function. The functional logic, the algorithms, and the equations to be used to implement these general requirements are contained in 3.4.

3.3.4.1 Channel management.- Channel management shall regulate the use of the RF channel by the Mode S sensor; it shall determine the nature and timing of each event to accomplish the required Mode S sensor surveillance and communication tasks. To provide surveillance of both ATCRBS and Mode S equipped aircraft with minimal interference, the RF channel shall be time shared between the ATCRBS-only All-Call mode, ATCRBS/Mode S All-Call mode, ATCRBS mode, Mode S-only All- Call mode, and the Mode S roll-call mode. In order to provide a maximum of channel time for Mode S activity, the nominal ATCRBS interrogation rate per mode (i.e., A and C) per antenna beamwidth shall be two. The intervals of time devoted to roll-call activity are defined as Mode S periods. Mode S roll-call interrogations shall be addressed to Mode S equipped aircraft under active surveillance (i.e., within the antenna beam). Channel time allocations for each Mode S interrogation and reply shall be based upon a prediction of aircraft range. Channel time shall be scheduled into time periods during which aircraft interrogations are made, or during which aircraft replies are received, so that surveillance and communication tasks of the sensor are carried out for each aircraft while it is under active surveillance. Mode S surveillance and data-link procedures may require more than one interrogation to each aircraft. Therefore, the channel management function shall be able to reinterrogate Mode S -equipped aircraft while in the antenna beam. Channel management shall maintain an active target list, comprised of those Mode S targets that are under active surveillance.

During a Mode S period one or more roll-call schedules shall be produced as required. A schedule is a set of interrogations and reply times (i.e., transactions), which allow channel management to complete one transaction per target to some or all of the targets on the active target list. The interrogations shall be timed so that nonoverlapping blocks of channel time are assigned to each individual interrogation and reply. If insufficient time is available to schedule all targets on the list, the time is allocated to targets according to preassigned transaction priority. The major channel management functions are channel control, transaction preparation, target list update, roll-call scheduling, and transaction update.

3.3.4.1.1 Channel control.- All activities that relate directly to the use of the RF channel shall be scheduled and directed by the channel control function. A time-out function shall be provided to ensure that the channel does not enter a nonterminating wait due to a failure. Channel control shall be responsible for the timely execution of all RF channel activities including Mode S Roll-Call, ATCRBS/Mode S All-Call, ATCRBS Only All-Call, ATCRBS, and Mode S Only All-Call interrogations. Channel control shall perform ATCRBS/Mode S period scheduling such that a periodic structure of Mode S and ATCRBS/All-Call periods is imposed on the real-time line. The repetition period of this structure is called the frame time, and the patterned time interval, whose duration is the frame time, is called a frame. A frame contains one or more ATCRBS/All-Call periods and one or more Mode S periods. Each sensor shall always be cognizant of the particular frame structure in use at any given time. Channel control shall generate any desired mode interlace pattern, with ATCRBS/Mode S All-Call, ATCRBS-only All-Call or ATCRBS interrogations.

3.3.4.1.2 Transaction preparation.- Under channel control, the transaction preparation function shall provide a list of targets that are about to come under active surveillance. All uplink message data and downlink message requests shall be taken into account in determining the number and type of transactions to be prepared by this function. Transaction message data shall be prepared in a manner that satisfies (where appropriate) the message requirements (e.g., protocol, multisite protocol, etc.)

contained in the Mode S National Standard. The transaction preparation function under channel control, shall provide a time-ordered list of transactions (i.e., interrogation reply pairings for an aircraft) for those aircraft that are about to come under active surveillance. This data shall be structured to facilitate data retrieval.

3.3.4.1.3 Target list update.- Target list update shall operate under the control of the channel control function. The target list update function shall merge the list of transactions (for new aircraft coming into the antenna beam) as described in 3.3.4.1.2 with the list of transactions for aircraft currently in the beam, and remove aircraft that are no longer under active surveillance or those that have been completely serviced.

3.3.4.1.4 Roll-call scheduling.- This function shall operate under the direction of channel control. The roll-call scheduling function shall operate on the list of aircraft on the active target list (3.3.4.1.3) to produce a schedule. The schedule shall be composed of interrogation and reply periods which fit into the available channel time. If there is insufficient time to schedule at least one transaction each for all aircraft on the active target list, available time shall be allocated based on five levels of transaction priority as follows:

Level 1 - Surveillance and high priority standard messages;

Level 2 - High priority uplink extended length messages (ELMs);

Level 3 - Additional standard (lower priority) messages;

Level 4 - Uplink ELMs;

Level 5 - Downlink ELMs.

Those aircraft with an unsuccessful transaction and which are still under active surveillance, shall be rescheduled, where possible, to complete the unsuccessful transaction prior to any other transaction (for that aircraft) and prior to the aircraft's transition to the inactive surveillance state; these interrogations shall be at a higher transmitter power level (selectable by parameter).

3.3.4.1.5 Transaction update.- Under the direction of the channel control function (3.3.4.1.1) the transaction update function shall examine each aircraft reply, and if the transaction is successful, modify that aircraft's transaction schedule such that the next pending transaction shall be carried out in the next schedule. If the transaction was not successful, it shall be repeated in the next schedule and the subsequent pending transaction (for that aircraft) shall be delayed to a later schedule. Transaction update shall direct the transfer of all Mode S replies, as they become available from the Mode S reply processor, to data link processing and surveillance processing. Those aircraft on the active target list that have no transactions pending shall be so labeled.

3.3.4.2 Transmitter/modulator unit.- The transmitter/modulator unit shall accept all digital control inputs from channel management and generate the required RF interrogation signals. For each interrogation to be transmitted, the control inputs shall specify the transmission type (3.3.4.2.1), the power mode, the transmission time, and for a Mode S interrogation, the contents of ‘the Mode S data block. The RF signal contents (coding, parity encoding, etc.) and waveform fidelity shall be in accordance with the Mode S and ATCRBS National Standards. High energy switching for modulation functions shall not be employed. The modulation circuitry shall be protected against active transmitter device arcing, shorting or other modes of failure.

3.3.4.2.1 Transmission types.- The transmitter/modulation unit shall be capable of transmitting the following interrogation types upon command from channel control:

(1) ATCRBS Mode A/Mode S All-Call;

(2) ATCRBS Mode C/Mode S All-Call;

(3) Military Mode 2;

(4) Mode S Only All Call;

(5) ATCRBS Mode A Only All-Call;

(6) ATCRBS Mode C Only All-Call;

(7) Mode S Short Roll-Call;

(8) Mode S Long Roll-Call;

(9) ATCRBS Mode A;

(10) ATCRBS Mode B;

(11) ATCRBS Mode C;

(12) ATCRBS Mode D.

3.3.4.2.2 Transmitter.- Each channel shall include two transmitters, primary and auxiliary. The primary transmitter shall be used for all main-beam transmissions. SLS control transmissions shall be generated by the auxiliary transmitter.

3.3.4.2.2.1 Primary transmitter.- The primary transmitter shall operate in three modes: a high-power Mode S mode, a low-power Mode S mode, and an ATCRBS mode. Both Mode S modes shall be capable of handling all of the Mode S interrogation types defined in the Mode S National Standard including extended length message (ELM) transmissions. ATCRBS/Mode S All-Call interrogations, ATCRBS-only All Call interrogations, Mode S Only All-Call interrogations, and military Mode 2 and ATCRBS interrogations are transmitted at the ATCRBS power level. All other interrogations are transmitted at either the Mode S-high or Mode S-low power level, the selection being determined by channel control. A common transmitter design shall be used for Mode S Type I, II, and III sensors (1.2.1).

3.3.4.2.2.2 Auxiliary transmitter.- The auxiliary transmitter shall generate the P5 pulse for Mode S SLS as well as the P2 or P1 and P2 pulses for ATCRBS SLS or improved ISLS. It shall be automatically controlled to follow the primary transmitter independent of interrogation type in the sense that for a particular interrogation, the peak auxiliary power equals the peak primary power plus a constant which is manually controllable over a range in steps. The auxiliary transmitter shall follow this nominal performance within a specified tolerance. The duty factor of the auxiliary transmitter shall be consistent with the specified interrogation rates for the primary transmitter.

3.3.4.3 Multichannel receiver.- The multichannel receiver shall process the RF signals which are input from the Mode S Sensor antenna subsystem to provide video and two-level quantized video signals to both the Mode S and ATCRBS reply processors. The sensor antenna subsystem shall consist of three channels, each of which has a different azimuthal coverage pattern and gain. These three channels are:

1) Sum or symmetrical pattern channel (Σ);

2) Difference or antisymmetrical pattern channel (∆);

3) Omnidirectional pattern channel (Ω).

These three signals shall be processed by the multichannel receiver to provide signals that can be used for reply detection, reply resolution, discrimination of side and back lobe replies, and off-boresight angle-of-arrival (monopulse) estimation. The multichannel receiver shall preserve the amplitude and phase fidelity as well as the dynamic range of the received signals in order to achieve the specified range and monopulse accuracies.

3.3.4.3.1 Reply pulse processing.- The multichannel receiver shall provide the following video output signals for use by the ATCRBS and Mode S reply processors:

1) a quantized sum (Σ) antenna pattern signal whose detection threshold depends on one of three separately adjustable parameters: a fixed threshold parameter, a signal amplitude-dependent parameter, and a time-varying parameter;

2) a quantized signal to indicate when the slope of the sum (Σ) antenna pattern signal exceeds a preset rate, one for the positive direction and one for the negative direction;

3) a quantized signal to indicate pulse reception in either sidelobe or backlobe of the antenna pattern;

4) a monopulse, bipolar video signal proportional to the off-boresite azimuth angle;

5) a signal proportional to the sum (Σ) antenna pattern (Mode S processor only).

The signal dependent threshold parameter in 1) above, is provided to reduce the likelihood of detecting low-level multipath replies. Multipath rejection shall be accomplished by referring the detection threshold (in 1) above) to the amplitude of the detected pulse. The time varying threshold in 1) above shall be provided to minimize occurrence of false replies arising from nearby reflectors. This threshold shall be site adaptable. The output signals and their corresponding threshold detection parameters in 1) and 3) above shall be tailored to provide one set of signals (and parameters) for ATCRBS replies and one set of signals (and parameters) for Mode S replies.

3.3.4.4 Mode S reply processing.- The Mode S reply processing system shall operate on the multichannel receiver outputs, (quantized sum (Σ) signal, quantized sum (Σ) positive and negative slope signals, quantized SLS signal, monopulse video, and the sum (Σ) signal) to detect Mode S roll-call and :All-Call replies; to provide estimates of their range and azimuth; and to decode their message blocks. Mode S replies employ parity encoding which shall be utilized by the reply processor to detect and correct errors. The Mode S reply processor shall generate a digitized representation of the quantized video signals which preserves Mode S sensor accuracy, in a format appropriate for reply detection and processing. The reply signals and formats will be in accordance with the Mode S National Standard. Upon processing All-Call replies and roll-call replies the processor shall prepare target reports containing each target's pertinent information.

3.3.4.4.1 Preamble detection.- Mode S replies shall be detected based on the four-pulse preamble waveform preceding the reply data block. A preamble shall be declared when valid pulses are detected in all four positions of the preamble waveform and, in addition, at least two of the pulses are detected with clear leading edges. A reply shall be accepted only if its preamble is detected within a listening ‘window’ surrounding its expected (predicted) reply time. This ‘window’ minimizes the probability of missing the desired reply due to ATCRBS fruit. If no preamble is detected within the ‘window’, the processor shall output a signal to denote this event (3.4.4.8.2). Target range estimation shall be based on the arrival time of the leading edge of the first pulse of an accepted Mode S preamble relative to the start of the listening ‘window’.

3.3.4.4.2 Message bit processing.- Message bit processing shall process the appropriate digitized multichannel receiver signals corresponding to the data block of an accepted Mode S reply and produce a message…