GPS Flexible Power Coming on September 7

September 2, 2010 By: Don Jewell

From September 7 to September 11, Air Force Space Command (AFSPC) will conduct what I like to call a "Tim the Tool Man Taylor" more-power exercise, which they have chosen to more appropriately call a Flex-Power Space and Control Segment Integration Checkout.

I hear you asking, what the heck does that mean? It means that the GPS ground command segment at Schriever Air Force Base in Colorado will slightly increase the power on several GPS satellites to test receiver equipment and the satellites to determine how the extra power is tolerated. Several ground and anechoic chamber tests have already been conducted over a period spanning several years, with virtually no negative affects. But experience has taught the GPS Wing and the 50th Space Wing, where the Second Space Operations Squadron (2 SOPS) resides, to go slow in these matters and make sure they aren’t disrupting GPS receivers that might have a problem with the increased power.

Officially, the flex power assessment will ensure that the GPS control segment baseline (AEP 5.5) is properly integrated with the space segment with regard to command and control of High-Y Flex Power — a capability that increases the nominal transmit power of the desired signal by shifting power between signals (M-code and P(Y)) within a particular L-band. The net sum gain remains the same. High-Y Flex Power does not change total transmit power, does not affect phase stability between L1 and L2, is ICD-GPS-200E compliant, and does not affect the navigation message.

So as long as your GPS receiver is IS-GPS-200E compliant, then you have nothing to worry about. How do you know if it is compliant? You probably don’t, and short of reading the very fine print in your owner's manual or calling up your receiver manufacturer, you will just have to assume it is compliant, as the majority of receivers, probably in the 98 percentile, are today.

While the primary objective of the Flex Power Exercise will be to ensure the flex power mode control functionality has been implemented correctly and all supporting procedures and documentation allow operators full operational control, for users the real purpose of the exercise is that it will provide an opportunity for the user equipment community (military, civil, and commercial) to evaluate the benefits of flex power on signal availability and improved accuracy. To this end, several organizations are placing receiver equipment in various locations to collect data during the event. The GPS Wing has interfaced with these organizations to receive the analysis derived from the data collection.

AFSPC has proactively engaged with key military, civilian, and commercial GPS users, operators, and manufacturers to ensure full awareness of the flex power demonstration, to make sure that their concerns are addressed, and that they have a clearly defined avenue to quickly identify and resolve any unforeseen issues that may arise during testing.

What do you do if you do experience a problem during this phased flex power test?

First, I recommend that you reboot your receiver, determine the satellites that are affecting your receiver, and then call the appropriate agency for your circumstances. For civilian and commercial users, contact the Coast Guard Navigation Center 24/7, and for military and government users contact the GPSOC, also 24/7. Contact information is listed below.

No one really expects any problems to occur, and this should really be a non-event for all users, but just in case we wanted to make sure to get the word out.

Points of Contact:

Civilian: NAVCEN at 703-313-5900
Military: GPS Operations Center at http://gps.afspc.af.mil
DSN 560-2541,
COMM 719-567-2541, Email: gps_support@schriever.af.mil,
https://gps.afspc.af.mil
Military alternate: Joint Space Operations Center, DSN 276-3514,
COMM 805-606-3514, jspoccombatops@vandenberg.af.mil

Afterwards, if you have any great stories to tell or if it was just a yawn for you, drop me a line and let me know what you thought of flex power. Did it allow you to sync-up faster? Did you have a noticeably stronger signal? Were there any problems? Let us know at: djewell@quextex.com

Happy navigating, more power to you!