GPS AEP 5.5C, the Rest of the Story: We Went to the Source

February 24, 2010 By: Don Jewell

GNSS Design & Test Newsletter, February 2010

If you are interested in the Global Positioning System (GPS) and are not related to Rip Van Winkle, then you have heard about the controversy surrounding the latest AEP ground control segment software upgrade, designated as version 5.5C.

Shortly after the upgrade occurred on January 11, a specific subset of GPS SAASM (Selective Availability Anti-Spoofing Module) equipped receivers installed in military platforms started experiencing problems. To say much more than that goes beyond the unclassified venue of this interview; suffice it to say there were intermittent and somewhat unpredictable problems and the GPS Wing immediately started working with the receiver manufacturer(s) involved to assess the impact and determine the root cause.

We are now six weeks out from the time the problems were first reported and the initial temporary fixes are on the street with permanent solutions close behind.

As you can imagine and may have read, the speculation surrounding the cause and extent of the problems to GPS have been almost mind-boggling. Everybody and their brother have their own opinion, which they swear is straight from the horse’s mouth. And of course a lot of what has been written is pure speculation combined with a great deal of “just getting the facts wrong.” Including intense speculation that the AEP update caused more than one specific problem. The truth is there was a later episodic problem that was totally unrelated to the AEP update.

So to remedy the speculation problem, we went straight to the source and asked the GPS Wing for an interview to discuss the much discussed AEP 5.5C upgrade.

We (Alan Cameron, editor-in-chief of GPS World, and Don Jewell, GPS World Defense PNT contributing editor) had a conference call with Colonel David Madden, the GPS Wing Commander; Colonel David Goldstein, the GPS Wing Chief Engineer; and Colonel David Buckman, the HQ AFSPC Command Lead for PNT, Position, Navigation and Timing. It was one of those rare instances where when you said, Hey Dave, three people answered.

We did not pull any punches with our questions, and to their credit the Daves were upfront and straightforward with their answers. We really believe the GPS Wing and USAF in general is tired of all the speculation and wanted everyone to know exactly what happened. We are happy to oblige.

GPS World Interview Questions with Responses

Don Jewell (DJ): What is the status of the AEP 5.5C update?

Colonel David Madden, GPS Wing Commander (CM): AEP 5.5C is currently flying the GPS constellation and is performing as expected. The GPS Wing has isolated the problem with military receivers down to a small subset of SAASM receivers. The GPS Wing is currently working with the user community to install a temporary fix to these receivers while a permanent solution is tested and certified.

DJ: How did the AEP 5.5 update issue manifest itself?

CM: A small subset of SAASM receivers began experiencing loss of GPS lock for several seconds or several minutes and, in very rare cases, could not acquire satellites until zeroized and reset.

DJ: Are there any plans to revert to AEP version 5.4 or would that cause more confusion and problems now that the switch to 5.5 has been made?

CM: There are no plans to revert to AEP 5.4. While reverting would have provided a temporary fix to the issue we’ve experienced, we have since determined that reverting would have caused unintended consequences to a different subset of SAASM receivers, so in retrospect, we made the right decision to stay the course with AEP 5.5C. So you’re correct, reverting would have caused more confusion as a different subset of receivers would have then experienced issues.

DJ: Dave, will the events caused by the 5.5C update delay 5.5D for further testing and communication with the military, commercial, and civil users and various receiver manufacturers?

CM: Pending senior leadership approval, and after we test a subset of military and commercial receivers with an AEP 5.5D generated NAV message/signal, AEP 5.5D will be installed as scheduled. And before you ask, we do not as yet have a firm date for that to happen.

DJ: Will there be changes or clarifications made to the receiver ICDs (Interface Control Documents) as a result of what you have discovered after this update?

CM: At this time, we don’t believe there are any changes or clarifications that need to be made to our receiver ICDs. We are, however, in the process of performing a detailed review to verify that no changes are needed.

DJ: There has been talk that there are some ambiguities in the current ICDs. Do you agree, and if so, will they be corrected or clarified?

CM: At this time, we don’t believe there are ambiguities in our receiver ICDs. And as I stated before, a review is under way to verify this.

DJ: What is the normal course of events and update cycle for the ICDs?

CM: ICDs are generally updated on an as-needed basis and are usually not updated more than every year. The first step is to identify what changes are needed. Then the Interface Control Coordinator (ICC) for the impacted ICDs will hold a series of meetings with the impacted stakeholders to draft the updated language. Once the language is finalized it generally takes about 60-90 days to go through the GPS Wing and prime contractor technical and contractual reviews before approval by the Configuration Control Board (CCB).

DJ: Now that sounds like quite a process. Is there an out-of-cycle ICD update capability?

CM: Yes. An ICD update can be processed as an emergency change. This will normally reduce the processing time between finalized language and CCB from about 60 days to less than 14 days.

DJ: What are your plans to make sure events like this do not happen in the future?

CM: Over the next several months the GPS Wing will conduct a bottom-ups review of our UE, or user equipment, test methodology and develop a set of lessons learned from these issues. The review will start with our GPS Integrated Test Team (ITT) meeting the last week of February 2010, where we will assess the current testing methodology to determine if and what changes we should seek to make.

DJ: There were other problems that occurred two weeks after the AEP 5.5C update with some SAASM receivers that concerned authentication. Are those problems resolved, and are you sure they were unrelated to the update? Can you give us the status on the way ahead with these receivers? It is rumored that it was an error code issue, which must mean that error codes among GPS manufacturers are not standardized. Would error code standardization prevent this from happening in the future? Any plans to go in that direction?

CM: The additional problems that cropped up two weeks after the AEP 5.5C update have been conclusively proven not to be related to the installation of AEP 5.5C. The SAASM vendor involved and the associated program offices are working hand-in-hand to develop, test, and field a fix to the affected receivers. Error codes are standardized across manufacturers, and no amount of further standardization, or even testing, would have prevented this second issue.

DJ: Dave, could better communication between the GPS Wing and the various user communities and receiver manufacturers as to your planned actions and how AEP 5.5C would affect various receivers have prevented this problem or issue in the first place?

CM: No, we do not think improved communication could have prevented this issue a priori. However, improved communication during the transition could have allowed us to isolate the issue more quickly. Moving forward, the GPS Wing will work with user-equipment manufacturers to improve communication during upgrades and transitions to ensure shorter coordination timelines in the event issues arise.

DJ: How is your working relationship with the affected receiver manufacturers?

CM: The GPS Wing has been working very closely with all receiver manufacturers, whether they’re affected or not. Manufacturers and users were involved in the creation and analysis of potential courses of action. Several manufacturers and DoD (Department of Defense) organizations have tested the GPS Wing’s temporary fix with great success.

DJ: Since you have such a good relationship with the affected receiver manufacturers, are you assisting them in their efforts to fix the problems, and if so, how?

CM: Yes, we are. In response to a direct tasker from the SMC (Space and Missile Systems Command) Commander (Lt. Gen. Tom Sheridan, USAF), the GPS Wing established a Crisis Action Team (CAT) with the mission to be the central point for research, coordination, and strategic communications surrounding the AEP 5.5C receiver issue. The results of this team’s efforts have been used up the chain of command to brief GPS enterprise and DoD leadership, as well as the user community, comprised of both government and industry organizations. The CAT has worked side-by-side with the affected receiver manufacturer since the discovery of this issue, and continues to coordinate and communicate with them on a daily basis.

DJ: Have you been able to accurately determine how many receiver models are affected?

CM: Yes, we know exactly how many receiver models are affected, and the impact to the platforms in which they are installed. However, these details will not be publicized.

DJ: Have you determined how many critical military, civil, and commercial systems have been affected?

CM: Yes, however, there are no civil/commercial systems affected as the affected receivers are limited to a subset of SAASM receivers.

DJ: OK, then what can you say about the SAASM receivers that were affected? Do SAASM receivers go through a more rigorous certification process than a civil or even standard non-SAASM-capable military receiver?

CM: Details of the currently affected SAASM receivers cannot be released for operational reasons. The only GPSW certification that SAASM receivers undergo is a security certification. This process is rigorous in ensuring that classified information is not compromised by the SAASM receiver manufacturer. However, the GPS Wing does not currently evaluate or certify SAASM receivers for performance or ICD compliance. Individual government procurement offices are responsible for establishing test programs to ensure compliance with published GPS ICDs or Interface Specifications.

DJ: Is there a work-around in place for the critical military systems that are affected?

CM: Yes, many of the platforms that have affected receivers installed are not experiencing any impact due to the robust nature of their installation. Those platforms experiencing impacts are being provided a temporary fix, or have developed tactics, techniques, and/or procedures as a work-around. Again, civil and commercial users are not affected by this issue.

DJ: Do you have a get-well date for all the military systems affected?

CM: We are currently working on software updates to the affected receivers; the software will be available to the integrators over the next several months. There is currently no forecast get-well date for all receivers, as the permanent fix has not been fully tested and certified.

DJ: How has this event affected our warfighters in the AOR (Area of Responsibility)?

CM: Across the DoD, impacts to warfighters have been minimal. Two classes of impacts are seen, first to systems in development and second to operational systems. The bulk of the systems impacted are in development. Currently, systems in development are more significantly impacted because receivers and platforms are more thoroughly instrumented during testing, and the receiver issue is observed and can impact development testing and schedules. As stated previously, operational systems typically have robust/redundant navigation systems, and the way this issue manifests itself does not negatively impact platform missions. Furthermore, in most cases, operational systems aren’t even noticing the issue.

DJ: That partially answers my next question. Were the deaths of 10 civilians in a building destroyed in Afghanistan a few days ago, by a GPS-directed rocket system, in any way related to the military SAASM receiver problems caused by the AEP 5.5C update? The system in question is HIMARS (High Mobility Artillery Rocket System), which uses GPS-guided munitions. Use of that system has been suspended pending an investigation. Is a GPS receiver error suspected of contributing to this errant attack?

CM: Don, I’m sure you understand that we cannot provide information related to an ongoing investigation. I can tell you, however, that we are confident the GPS receiver error did not contribute to this tragic occurrence. The Los Angeles Times reported on February 18, 2010, that the military authorities in Afghanistan have reported the HIMARS weapons system did function normally and are focusing their investigation on why that particular building was targeted.

DJ: Thanks, Dave, that’s good to know. Now, will the problems encountered with the last update affect the current schedule for OTAR (over-the-air re-keying) roll out and GPS IIF support capabilities?

CM: Additional testing will be conducted prior to “rolling out” SAASM capabilities such as OTAR; however, schedule slips should only be on the order of a few months.

DJ: Dave, since this was a problem initiated by a GPS control segment software update, can you elaborate on the way ahead for the GPS control segment? Specifically future updates; OCX (next-generation control segment, the contract for which should be awarded this week); more communication with users; more modeling, testing, and certification of civil, commercial, and military receivers.

CM: We expect to announce the results of the OCX Phase B down select before the end of the month. This will allow us to move out with developing the next-generation GPS control segment. The issues we have had with the UE (user equipment) have certainly made us more aware of the challenges we face when integrating space, ground, and UE together to field a new capability. We will apply the lessons learned here when we field GPSIII, MGUE, and OCX for the modernized signals. Since the GPS Wing procures a very small percentage of all military receivers, over the next several months the GPS Wing will investigate obtaining a broader subset of civil, commercial, and military receivers in order to instrument and integrate them into DoD lab receiver test racks. In addition, the GPS Wing will investigate the generation of higher fidelity models of control segment upgrades for use in commercial and military simulation systems.

DJ: Have you considered the idea of a separate voluntary GPS certification receiver authority, similar to the work the Underwriters Laboratories (UL) undertake today for electronics and appliances?

CM: Yes. A separate GPS receiver certification authority is certainly of high interest to both the GPS Wing and the GPS community. However, no final decision for the implementation of this has yet been made.

DJ: What will you do differently this time around for the upcoming AEP 5.5D update?

CM: No firm date has been set for the installation of AEP V5.5D. We are working with the 50th Space Wing, 14th Air Force and Headquarters Air Force Space Command (AFSPC) to gain concurrence to install AEP V5.5D. However, AEP V5.5D is a minor upgrade to AEP V5.5C to provide last-minute changes that enables us to fly GPS IIF-1 and check out its NDS payload. It is a sustainment build and it does not affect the NAV message content. Hence, only the standard ground segment system test / regression testing have been performed on this release.

DJ: What message do you want the world to know about GPS? Is there a message you want to deliver concerning GPS viability, capability, and integrity?

CM: The GPS constellation continues to perform at or above specifications. GPS viability, capability, and performance have never been better.

DJ: Do you think global confidence in the GPS has been affected by the latest incidents, and what is the plan to recover public confidence?

CM: The 3/4 of a billion GPS users can and should remain confident in the continued quality service GPS provides. We are working hard with our control segment and user equipment manufacturers to ensure issues like this do not occur again.

DJ: Great! What do you see as the future for GPS?

CM: The Air Force will continue to focus on maintaining GPS as the premier provider of positioning, navigation, and timing (PNT) for military, commercial, and civilian users around the world. The Air Force is committed to providing uninterrupted GPS service, at or above our performance commitments for decades to come. The benefits of the new AEP software include enabling the ground system that controls the GPS constellation to command the new GPS IIF satellite family, the first of which will be launched in May 2010. New capabilities being brought online with the launch of the IIF satellites will include a new navigation signal for civil users, encrypted military code, crosslink enhancements, improved navigation signal accuracy and signal power increases. The new AEP software also provides robust security improvements to include "over-the-air" distribution of encryption keys to properly equipped military users. The Air Force is on-track to launch the first GPS IIF spacecraft, develop and field GPS III, actively conduct technical demonstrations and risk reduction for our next-generation Military GPS User Equipment (MGUE), and define a creative MGUE acquisition strategy based on a Common GPS Module (CGM). Most importantly, the GPS Wing is working closely with Air Force Space Command Headquarters and Operations teams at Cape Canaveral Air Force Station and Schreiver Air Force Base to successfully sustain and enhance GPS mission capabilities — providing the most robust GPS on-orbit constellation ever for warfighters and civil users worldwide.

DJ: Dave, that is a great summary and look at the way ahead. Any closing comments?

CM: Don, there are always going to be challenges when upgrading a system of this magnitude, but the Air Force is committed to ensuring we continue to meet our service commitments. Of note, less than 1 percent of GPS SAASM military receivers experienced this anomaly and none of the hundreds of millions of commercial users were affected. We anticipate a fix will be in place within several months. As soon as the permanent fix is tested and certified, modifications to platforms with affected receivers will begin. The GPS constellation remains healthy, stable, and robust with 30 operational satellites broadcasting positioning, navigation and timing information for military and civilian users around the world. Older yet usable satellites are placed in a holding orbit so they can be reactivated, if necessary, and we have established a power management procedure to ensure existing satellites continue their performance and primary function. We’re making steady progress in synchronizing the spacecraft, the control segment, and user equipment to ensure users will be able to take advantage of the capability on orbit as well as on the ground. The Air Force is committed to maintaining the current level of service while striving to improve the GPS system as we sustain and modernize it into the future. The Air Force will continue to pursue an achievable path maintaining GPS as the premier provider of positioning, navigation, and timing for the military and civilian users around the world. GPS will be there for us as we need it.