Joint Precision Approach and Landing System
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The Joint Precision Approach and Landing System (JPALS) is a military, all-weather landing system based on real-time differential correction of the GPS signal, augmented with a local area correction message, and transmitted to the user via secure means. The onboard receiver compares the current GPS-derived position with the local correction signal, deriving a highly accurate three-dimensional position capable of being used for all-weather approaches via an ILS-style display. While JPALS is similar to Local Area Augmentation System, but intended primarily for use by the military, some elements of JPALS may eventually see their way into civilian use to help protect high-value civilian operations against unauthorized signal alteration.
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[edit] History
The need for JPALS was identified in response to two factors. First, the military needs an all-service, highly mobile all-weather precision approach system, tailorable to a wide range of environments, from shipboard use to rapid installation at austere airfields. Second, they need a robust system that maintains a high level of reliance in combat operations, particularly, one that's highly resistant to jamming.
[edit] Operation
JPALS encompasses two main categories: SRGPS and LDGPS. SRGPS provides highly accurate approach positioning for operations aboard ship, including aircraft carriers, helo and S/VTOL carriers, and other shipboard operations, primarily, but not limited to, helicopter operations.
LDGPS is further divided into three sub-categories: Fixed Base, Tactical, and Special Missions. Fixed Base is used for ongoing operations at military airfields around the world, while the Tactical system is a portable system, designed for relatively short-term, austere airfield operations. The Special Missions system a highly portable system capable of rapid installation and use.
[edit] Accuracy
The accuracy of LAAS, or Local Area Augmentation System, is better than CAT III ILS accuracy, and will provide horizontal and vertical resolutions of less than 1 m. Although the exact accuracy of JPALS will remain classified, it's estimated that JPALS will meet or exceed this accuracy for authorized users.
[edit] Benefits
The main benefit of JPALS is that it's a system that can be taken anywhere, anytime, providing a safe and effective way to conduct 24/7, all-weather, anti-jam instrument landing system capability to all authorized users, worldwide. A secondary benefit is a significant reduction in cost savings over current systems.
The naval version of JPALS transmits a signal that has a low probability of intercept. Meaning it is unlikely that an enemy will detect the signal and trace it back to its source. The existing system, TACAN, is not encrypted or concealed in any way and basically tells the enemy the bearing and range of the ship installed on. This is not acceptable if emissions control (EMCON) or stealth are required.
The increase in both accuracy and reliability will significantly enhance operations while reducing non-operational periods due to weather or adversarial efforts, with significant cost savings as a side benefit.
[edit] See also
- Local Area Augmentation System is a similar system for civilian usage.
- Wide Area Augmentation System
- Precision approach
- Instrument Landing System
- Global Positioning System
- Differential GPS
| Satellite navigation systems |
 Transit | GPS |  GLONASS |  Galileo |  Beidou |
| Related topics: EGNOS | WAAS | LAAS |
[edit] References
- Federal Aviation Administration (FAA) (February 27, 2004). Local Area Augmentation System (LAAS) Fact Sheet. Retrieved on November 20, 2005.
- Department of Transportation and Department of Defense (March 25, 2002). 2001 Federal Radionavigation Plan (PDF). Retrieved on November 27, 2005.
