Selective availability anti-spoofing module
Feature of the Global Positioning System
A Selective Availability Anti-spoofing Module (SAASM) is used by military Global Positioning System receivers to allow decryption of precision GPS observations, while the accuracy of civilian GPS receivers may be reduced by the United States military through Selective Availability (SA) and anti-spoofing (AS). However, on May 1, 2000 it was announced that SA was being discontinued, along with a United States Presidential Directive that no future GPS programs will include it. Before the advent of L2C, AS was meant to prevent access to dual-frequency observations to civilian users.
SAASM allows satellite authentication, over-the-air rekeying, and contingency recovery. Those features are not available with the similar, but older, PPS-SM (Precise Positioning Service Security Module) system. PPS-SM systems require periodic updates with a classified "Red Key" that may only be transmitted by secure means (such as physically taking the receiver to a secure facility for rekeying or having a trusted courier deliver a paper tape with a new key to the receiver, after which that paper tape must be securely destroyed). SAASM systems can be updated with an encrypted "Black Key" that may be transmitted over unclassified channels. All military receivers newly deployed after the end of September 2006 must use SAASM.
SAASM does not provide any additional anti-jam capability, however, the higher data (chipping) rate of P(Y) code can provide a higher processing gain which will provide better tracking performance in a jamming environment. Future GPS upgrades, such as M-Code, will provide additional improvements to anti-jam capabilities.
SAASM hardware is covered with an anti-tampering coating, to deter analysis of their internal operation.
The public source identifies “Selective availability anti-spoofing module” as feature of the Global Positioning System. This brief keeps that definition visible, then builds a research path around Selective, availability and anti-spoofing.
Why this record matters
A short description can identify a subject without explaining its stakes. For “Selective availability anti-spoofing module”, the useful work is to connect “feature of the Global Positioning System” to the records capable of establishing context and consequence.
Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Sep 21, 2023. The linked authority identifier is Q7447754. None of the 0 selected statements returned an explicit reference. The first chronological checks are 2000 and 2006.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Selective availability anti-spoofing module”, its source revision and the description used here.
- Expand the search: follow Selective availability anti-spoofing module primary sources, Selective availability anti-spoofing module archive and Selective research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Selective availability anti-spoofing module”?
- What terminology or title could unlock a more precise catalogue search?
- Which institution is responsible for the underlying evidence?
Search terms from this dossier
This entry incorporates text from “Selective availability anti-spoofing module” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.