Upgrade of GPS Control System to Be Tested

Upgrade of GPS Control System to Be Tested
http://www.gpsworld.com/gnss-system/news/upgrade-gps-control-system-be-te=
sted-9063?print=3D1
October 22, 2009

You may have seen the somewhat cryptic NANU, a Notice Advisory to Navstar=
Users, issued by=20
the Air Force=E2=80=99s 2nd Space Operations Squadron (2SOPS) a few days =
ago:

TWO SVS WILL BE USED FOR TESTING IN A HEALTHY STATUS DURING UPCOMING TE#4=
=2E SVN 30/PRN 30=20
WILL BE USED ON 29 OCTOBER/J302 AND SVN 54/PRN 18 WILL BE USED ON 30 OCTO=
BER/J303.

This general message to all GPS users was accompanied by a series of NANU=
s forecasting=20
outages of PRN30 and PRN18 over a two-week period extending from 23 Octob=
er to 4 November.

So, what is =E2=80=9CTE#4=E2=80=9D and why are PRN30 and PRN18 being used=
?

TE#4 is Transition Exercise #4 and refers to testing of a new version of =
the Architecture=20
Evolution Plan (AEP) =E2=80=94 the new GPS control segment and its associ=
ated software. The=20
current software version operated at Schriever AFB is 5.4. TE#4 involves =
the transition to=20
AEP 5.5. As described by Lt. Col. Deanna Burt, commander of 2 SOPS, =E2=80=
=9CAEP 5.5 brings on=20
line the ability to command and control the new IIF satellites as well as=
an over the air=20
rekey and distribution system for our military P(Y) users. This alleviat=
es the=20
requirement for military users to carry a paper [cryptographic] key and t=
o have to=20
continually reload to gain access to the P(Y) code.=E2=80=9D

Testing of AEP 5.5 will be carried out from the Alternate Master Control =
Station at=20
Vandenberg AFB using two satellites, PRN30 and PRN18. These two satellite=
s will be set=20
unhealthy at times during the test period. PRN30 is a Block IIA satellite=
while PRN18 is a=20
non-modernized Block IIR satellite. According to Lt. Col. Burt, these two=
satellites were=20
chosen based on position dilution of precision calculations to ensure tha=
t the outages=20
would not significantly impact the user community.

TE#4 is the last development checkout of AEP 5.5 before 2 SOPS goes live =
with the new=20
software in late November. The testing over the next two weeks will ensur=
e that all=20
aspects of the software have been thoroughly checked so that when it goes=
on line it will=20
be transparent to users.

Software version 5.5 is the last major software modification in the AEP.