NTS-2 wasn't a GPS satellite, but it did
http://www.ipgp.fr/~tarantola/Files/Professional/GPS/Neil_Ashby_Relativity_GPS.pdf
"At a radius of 9550 km, about 3000 km above the ground, the
gravitational and Doppler effects cancel. Because the GPS orbits are
higher than that, the gravitational blueshift
is the largest contribution. So the net frequency correction for a GPS
satellite is negative, amounting to 4.4645 parts per ten billion.
Nowadays the rate of every orbiting GPS clock is adjusted by this
"factory offset" before launch. But before the first GPS satellite was
launched in 1977, although it was recognized that orbiting clocks
would require such a relativistic offset, there was uncertainty as to
its magnitude, and even its sign. So correcting frequency
synthesizers were built into the clocks, spanning a large enough range
around the nominal 10.23 MHz clock frequency to encompass all
possibilities. After the satellite's cesium atomic clock was turned
on, it was operated for three weeks to measure its rate. The frequency
shift measured during this initial period was found to be 4.425 parts
per ten billion, agreeing with the relativistic calculation to better
than 1%."
http://relativity.livingreviews.org/Articles/lrr-2003-1/download/lrr-2003-1Color.pdf
"There is an interesting story about this frequency offset. At the
time of launch of the NTS-2 satellite (23 June 1977), which contained
the first Cesium atomic clock to be placed in orbit, it was recognized
that orbiting clocks would require a relativistic correction, but
there was uncertainty as to its magnitude as well as its sign. Indeed,
there were some who doubted that relativistic effects were truths that
would need to be incorporated [5]! A frequency synthesizer was built
into the satellite clock system so that after launch, if in fact the
rate of the clock in its final orbit was that predicted by general
relativity, then the synthesizer could be turned on, bringing the
clock to the coordinate rate necessary for operation. After the Cesium
clock was turned on in NTS-2, it was operated for about 20 days to
measure its clock rate before turning on the synthesizer [11]. The
frequency measured during that interval was +442.5 parts in 1012
compared to clocks on the ground, while general relativity predicted
+446.5 parts in 1012. The difference was well within the accuracy
capabilities of the orbiting clock. This then gave about a 1%
verification of the combined second-order Doppler and gravitational
frequency shift effects for a clock at 4.2 earth radii.
[5] Alley, C., “Proper time experiments in gravitational fields with
atomic clocks, aircraft, and laser light pulses”, in Meystre, P., and
Scully, M.O., eds., Quantum Optics, Experimental Gravitation, and
Measurement Theory, Proceedings of the NATO Advanced Study Institute
on Quantum Optics and Experimental General Relativity, August 1981,
Bad Windsheim, Germany, NATO Science Series: B, vol. 94, pp. 363–427,
(Plenum Press, New York, 1983).
[11] Buisson, J.A., Easton, R.L., and McCaskill, T.B., “Initial
Results of the NAVSTAR GPS NTS-2 Satellite”, in Rueger, L.J. et al.,
ed., 9th Annual Precise Time and Time Interval (PTTI) Applications and
Planning Meeting, Proceedings of the meeting, held at NASA Goddard
Space Flight Center, November 29 – December 1, 1977, pp. 177–200,
(Technical Information and Administrative Support Division, Goddard
Space Flight Center, Greenbelt, MD, 1978)."
Ref [11] :
http://www.pttimeeting.org/archivemeetings/1977papers/Vol%2009_13.pdf
"NTS-2 is the first NAVSTAR GPS Phase I Satellite . . . "
http://www.gpsworld.com/gnss-system/gps-modernization/the-origins-gps-part-1-9890?page_id=5
"NTS-II was launched on June 23, 1977, from Vandenberg Air Force Base.
Originally it was hoped that NTS-II would be a part of the initial GPS
test constellation. It could then have supplemented the satellites
being developed by Rockwell, providing another passive ranging signal
for the user equipment tests at Yuma Proving Ground. Unfortunately,
the NRL ranging transmitter in NTS-II failed prior to the launch of
the first JPO NDS satellites, rendering the NRL satellite unusable for
the Yuma Proving Ground testing."