# Presentation: 705407

## Ongoing Loran Evaluations at theFederal Aviation Administration and theUS Coast Guard Mitchell J. NarinsSystems EngineerFederal Aviation AdministrationNavigation Integrated Product Team

**Federal Radionavigation Plan**
**Public Meeting**
**FAA Headquarters, Washington, DC**
**19 May 2003**

## Purpose of the Evaluations

- To determine whether an enhanced Loran system can provide the:
**Accuracy**
**Availability**
**Integrity, and**
**Continuity**
- a) to support Lateral Navigation through all phases of flight – including Non-Precision Approach (NPA)
- b) to support Harbor Entrance and Approach (HEA) for maritime
- To determine what other ancillary benefits can be derived from the continued provision of enhanced Loran services
- e.g., to support Stratum 1 timing and frequency users
- To determine if provision of enhanced Loran services are cost-beneficial

## North American Loran System

## Government
FAA
Navigation Systems Engineering, AND-702
Navigation and Landing System Architecture, ASD-140
CNS Test and Evaluation, ACT-360
Flight Standards, AFS-400
Aircraft Certification, AIR-130
Special Programs, AVN-5
US Coast Guard 
Aids to Navigation
Navigation Center
Loran Support Unit
Volpe National Transportation System Center

- FAA
- Navigation Systems Engineering, AND-702
- Navigation and Landing System Architecture, ASD-140
- CNS Test and Evaluation, ACT-360
- Flight Standards, AFS-400
- Aircraft Certification, AIR-130
- Special Programs, AVN-5
- US Coast Guard
- Aids to Navigation
- Navigation Center
- Loran Support Unit
- Volpe National Transportation System Center

**Program Participants**

## Industry
Booz|Allen|Hamilton
Free Flight Systems
Illgen Simulation Technologies, Inc.
JJMA
Locus, Inc.
Megapulse, Inc.
Peterson Integrated Geopositioning
Reelektronika
Rockwell Collins
WR Systems

- Industry
- Booz|Allen|Hamilton
- Free Flight Systems
- Illgen Simulation Technologies, Inc.
- JJMA
- Locus, Inc.
- Megapulse, Inc.
- Peterson Integrated Geopositioning
- Reelektronika
- Rockwell Collins
- WR Systems

- Academia
- Ohio University
- Stanford University
- US Coast Guard Academy
- University of Rhode Island
- University of Alaska
- University of Wales

## Aviation Requirements: RNP* 0.3 (target); RNP* 0.5 (minimum)

_**Performance Requirement**_**	****	****	****   **_**Value**_
- Accuracy (target)				307 metersAccuracy (minimum)			802 meters
- Alarm Limit (target)				556 metersAlarm Limit (minimum)			926 meters
- Integrity					10-7/hour
- Time-to-alarm				10 seconds
- Availability (minimum)			    99.9%Availability (target)				    99.99%
- Continuity (minimum)			    99.9%Continuity (target)				    99.99%
- 				(Source:  FAA Loran Evaluation Report, June 2002)

***Required Navigation Performance**

## Marine HEA Requirements (Primary)

_**Performance Requirement**_** ****	****	****        ****	****     **_**Value**_
- Accuracy (target)				10 meters, 95%Accuracy (threshold)			20 meters, 95%
- Alarm Limit (target)		    	  	  25 metersAlarm Limit (threshold)			  50 meters
- Integrity (target)				     3x10-5
- Time-to-alarm				 10 seconds
- Availability (threshold)			     99.7%Availability (target/VTS)			     99.9%
- Continuity (threshold)		        99.85% over 3 hours
- 	Continuity (target)			        99.97% over 3 hours
- 	(Sources:  FRP, DOT Task Force, TASC DGPS Mission Needs Analysis: Harbor Entrance and 	Approach, IMO Resolutions A.815(19) and draft revisions to A.860(20))

## Marine HEA Requirements (Backup)

_**Performance Requirement**_**	****	****	****    **_**Value**_
- Accuracy (backup)				20 meters, 95%
- Alarm Limit (backup)			50 meters
- Integrity (target)				    3x10-5
- Time-to-alarm				10 seconds
- Availability (minimum)			    99.7%
- Continuity (minimum)		      99.85% (over 3 hours)
- 	(Sources:  FRP, DOT Task Force, TASC DGPS Mission Needs Analysis: Harbor Entrance and 	Approach, IMO Resolutions A.815(19) and draft revisions to A.860(20))

## Performance Specification 		               Value
Frequency Accuracy (threshold)    1 in 1012 (averaged over 24 hrs)
No External Antenna			 (desired)
Backward Compatibility			 (desired)
Integrity Data		           Minimum of USE/NO USE Flag 
Higher Accuracy Time of Day         Time Tag (Year/DOY/Second)
						  Leap Second information
Timing Accuracy				<100nsec
Differential Data			        Daily Correction

(Source:  DOT Task Force, T1X1 letter of Oct 2002)

- Frequency Accuracy (threshold)    1 in 1012 (averaged over 24 hrs)
- No External Antenna			 (desired)
- Backward Compatibility			 (desired)
- Integrity Data		           Minimum of USE/NO USE Flag
- Higher Accuracy Time of Day         Time Tag (Year/DOY/Second)
- 						  Leap Second information
- Timing Accuracy				<100nsec
- Differential Data			        Daily Correction
- (Source:  DOT Task Force, T1X1 letter of Oct 2002)

**Timing and Frequency Specifications**

## Timing User Spectrum

## Frequency User Range

## Loran-C Navigation Current Capabilities/Future Needs*

|  | Accuracy | Availability | Integrity | Continuity |
| --- | --- | --- | --- | --- |
| Current Definition of  Capability * (FRP) | 0.25 nm
(463 m) | 0.997 | 10 second alarm/
25m error | 0.997 |
| FAA NPA (RNP.3) Requirements | 0.16 nm
(307 m) | 0.999 – 0.9999 | 0.9999999 | 0.999 - 0.9999 |
| USCG Harbor Requirements 
(to date) | 0.004 - 0.01 nm
(8 – 20 m) | 0.997 - 0.999 | 10 second alarm/
25m error | 0.9985 – 0.9997 over 3 hours |

-   _Note_: Most stringent requirements shown in **aviation orange**.
- 	* Includes Stratum 1 timing and frequency capability.

## A Most Substantial Investment

## Status of Ongoing Loran Evaluations and System Recapitalization

**Final Report due to the Departments of Transportation and Homeland Security**
**March 2004**

***Accuracy***
***Availability***
***Integrity***
***Continuity***

## To determine Loran Accuracy Potential:
ASF* studies and calibration (for both conductivity and terrain)
Receiver/Integrated receiver studies
Loran Accuracy Performance Panel (LORAPP)
Differential Loran study
To determine Loran Availability Potential:
H-Field Antenna/P-static testing
CONUS All-in-view receiver analysis
Noise analysis
SSX and TFE modification evaluations
To determine Loran Integrity Potential:
Loran Integrity Performance Panel (LORIPP) 
Time of Transmission/ASF studies
To determine Loran Continuity Potential:
Receiver/Integrated receiver/antenna studies

- To determine Loran Accuracy Potential:
- ASF* studies and calibration (for both conductivity and terrain)
- Receiver/Integrated receiver studies
- Loran Accuracy Performance Panel (LORAPP)
- Differential Loran study
- To determine Loran Availability Potential:
- H-Field Antenna/P-static testing
- CONUS All-in-view receiver analysis
- Noise analysis
- SSX and TFE modification evaluations
- To determine Loran Integrity Potential:
- Loran Integrity Performance Panel (LORIPP)
- Time of Transmission/ASF studies
- To determine Loran Continuity Potential:
- Receiver/Integrated receiver/antenna studies

- *additional secondary factors

## Loran Issue 1: Accuracy

**Current Accuracy:             0.25 nm, 2drms, 95%**
**Target Accuracy (NPA):    0.16 nm (307 m) - RNP 0.3**
**	****	****	****	****	**** **** ****0.43 nm (802 m) - RNP 0.5**
**Target Accuracy (HEA):    8 – 20 m, 2drms, 95%**
**	****	****	****	****     **
**	****	**_**Issues**_**	****	****	**_**Potential Mitigations**_
- Old timing sources		 New cesium clocks
- Old timing equipment		 New timing suite
- Tube technology		 Solid State Transmitter                                                       (SSX) technology
- Simple propagation model	New ASF* tables/algorithms
- No real-time corrections	LORAPP (Differential Loran)
- 					                    *additional secondary factors

## Flights to support characterization of ASFsConducted in August 2002 and March 2003

## Typical Results

**NPA Requirement: 307 m !**

## Loran Issue 2: Availability

**Current Availability:**             **0.997**
**Target Availability (NPA):    0.999 - 0.9999**
**Target Availability (HEA):    0.997 – 0.999 **
**	****	**_**Issues**_**	****	****	**_**Potential Mitigations**_
- Precipitation Static		 H-Field Antenna*
- Atmospheric Noise		 H-Field, AIV Receiver
- Loss of Station Power	     	 UPS
- Lightning			 New Lightning Protection
- Chain/Stick Availability		 All-in-view receivers
- Tube overloads			 Solid State Transmitters
- 							*Awaiting safety certification

## Loran Issue 3: Integrity

**Current Integrity:       10 sec. alert @ **_**+**_** 100ns or other ****	****	****	****	****specified error conditions**
**Target Integrity (NPA):  0.9999999***
**	****	****	****	****	**** ****556m HPL, 10 sec. alert**
**Target Integrity (HEA):  0.99997****
- 		_**Issues**_**	****	**_**Potential Mitigations**_
- Presumed Integrity/	 Loran Integrity Panel (LORIPP)
- 	Auto Blink System	 Loran Accuracy Panel (LORAPP)

***For Aviation: The probability of providing Hazardous or ****	****       Misleading Information (HMI) is 1 x 10****-7**

****For Maritime: The probability of providing Hazardous or **
**	****         ****Misleading Information (HMI) is 3 x 10****-5**

## Status of Integrity (HMI) Analysis

**Results to date:**** **
- Developed initial algorithms and fault-trees
- Loran integrity
- Horizontal protection limit (HPL)
- Work continues
- Analyzed RNP 0.3 performance
- Appears feasible throughout CONUS
- May require changes in the system infrastructure, policy, processes, etc.
- May require continued operation of Canadian stations
- Work continues
- Analyzed RNP 0.3 approaches
- May be feasible with the improved infrastructure
- Work continues

## Loran Integrity Fault Tree

## Loran Issue 4: Continuity

**Current Continuity:  0.997**
**Target Continuity (NPA): 0.999 - 0.9999**
**Target Continuity (HEA): 0.9985 – 0.9997**
- 		_**Issues**_**	****	****	**_**Potential Mitigations**_
- Same as Availability plus:
- Receiver acquisition time	 New DSP technology
- 						 New SSX Switch Units
- 						 AIV/Integrated Receiver

## Loran Continuity Fault Tree

## Prototype Brassboard Locus Loran Card Installed in Rockwell Collins Multi-Mode Receiver 

**Flight Testing to begin this month**
**Integrated GPS/Loran receiver for general aviation also being developed by Free Flight Systems and Locus**

## Summary

- FY ’02 – Excellent progress, Goals achieved
- LORIPP is well on its way to showing that aviation integrity requirements can be met
- Flight tests showed that Loran can provide excellent accuracy (approaching GPS accuracies) when used in conjunction with appropriate ASF information
- FY ’03 – Work continues:
- Development of integrated prototype avionics and H-field antennas to evaluate Loran for all phases of flight in both stand-alone and multi-sensor configurations
- Development of better ASF models that include spatial factors based on both conductivity and terrain factors and temporal factors based on multiple seasonal measurements
- Publication of final H-Field/P-static test results
- Publication of interim LORIPP and LORAPP findings
- FY ’04 – Wrapping it up
- 31 March 2004 – Final Report due to DOT and DHS