21+3 space vehicles
Orbital height about 20,200 km (12 sidereal hours,
repeatibility
of the constellation every day four minutes earlier in UT)
Inclination of i=55 degrees, in six orbital planes
(A-F), separated 
degrees
Three types of satellites: Block I (1978-1985, development,
extincted), Block II (1989-1996, production, the most part of active
now) and Block IIR (1997-...replenishment, the new ones).
Block II: expected life is 7.5 years, 845 kg, the orbit
changes
usually last several weeks or months, ability to measure distance
between
satellites (Block IIR), two cesium and two rubidium frequency standard
per
satellite (accuracy of 
to 
.
Two carrier frequencies in L-band derived from the fundamental
frequency 
, L1: 
and
L2: 
.
C/A, P1 (Y1) codes and navigation
data
over L1 and P2 (Y2) and also navigation data over L2.