GPS System Segments - Understanding GPS: Principles and Applications - page 80

parameters to be saved to a special area of memory and reused following the load of
a new program. This feature reduces, by about 4 hours, the time required to recover
from a new program load. The SPU was provided with new rolling buffers to save
high-speed telemetry data for SV functions even when not in contact with the CS.

Improved Antenna Panel
Lockheed Martin, under an internal research and development effort, developed
new L-band and UHF antenna element designs. The new L1 power received on the
ground will be at least -154.5 dBW (edge-of-Earth, as compared to the current typi-
cal IIR performance of -155.5 dBW) and the new L2 power received on the ground
will be -159.5 dBW (edge-of-Earth, as compared to the current typical IIR perfor-
mance of -161.5 dBW). This provides greater signal power to the user. The last 4 of
the 12 classic IIRs and all of the modernized IIRs have the improved antenna panel.

Block IIR-M—Modernized Replenishment Satellites
The modernized GPS IIR (IIR-M) (see Figure 3.10) will bring new services to mili-
tary and civilian users [9, 10]. The IIR-M is the result of an effort to bring modern-
ized functionality to IIR SVs that were built several years ago and placed into
storage until they were needed for launch. The Air Force contracted Lockheed Mar-
tin in 2000 to modernize several of the unlaunched IIR SVs. This modernization
program has been accomplished within existing solar array capability, available
on-board processor margins, and current vehicle structural capabilities.
As many as eight Block IIR SVs will be modernized. Maintaining constellation
health could interfere with this goal, but current predictions are optimistic as the

Figure 3.10 Block IIR-M satellite. ( Source: Lockheed Martin Corp. Reprinted with permission.)