USA-145

{{Short description|American navigation satellite used for GPS}}

{{Infobox spaceflight

| name = USA-145

| image = GPS-IIR.jpg

| image_caption = A Block IIR GPS satellite

| insignia =

| mission_type = Navigation

| operator = US Air Force

| COSPAR_ID = 1999-055A{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1999-055A|title=Navstar 46|publisher=US National Space Science Data Center|access-date=11 July 2012}}

| SATCAT = 25933

| mission_duration = 10 years (planned)

| spacecraft =

| spacecraft_type = GPS Block IIR

| spacecraft_bus = AS-4000

| manufacturer = Lockheed Martin

| launch_mass = {{convert|2032|kg}}

| dimensions =

| power =

| launch_date = {{start-date|7 October 1999, 12:51:01|timezone=yes}} UTC

| launch_rocket = {{nowrap|Delta II 7925-9.5,}} D275

| launch_site = Cape Canaveral SLC-17A

| entered_service =

| disposal_type =

| deactivated =

| orbit_slot =

| orbit_epoch =

| orbit_reference = Geocentric

| orbit_regime = Medium Earth
(Semi-synchronous)

| orbit_periapsis = {{convert|20096|km|sp=us}}

| orbit_apoapsis = {{convert|20267|km|sp=us}}

| orbit_inclination = 53 degrees

| orbit_period = 717.96 minutes

| apsis = gee

}}

USA-145, also known as GPS IIR-3 and GPS SVN-46, is an American navigation satellite which forms part of the Global Positioning System. It was the third Block IIR GPS satellite to be launched, out of thirteen in the original configuration, and twenty one overall. It was built by Lockheed Martin, using the AS-4000 satellite bus.

USA-145 was launched at 12:51:01 UTC on 7 October 1999, atop a Delta II carrier rocket, flight number D275, flying in the 7925-9.5 configuration.{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|publisher=Jonathan's Space Page|first=Jonathan|last=McDowell|access-date=11 July 2012}} The launch took place from Space Launch Complex 17A at the Cape Canaveral Air Force Station,{{cite web|url=http://planet4589.org/space/lvdb/list2.html|title=Launch List|publisher=Jonathan's Space Page|work=Launch Vehicle Database|first=Jonathan|last=McDowell|access-date=11 July 2012|archive-date=15 August 2020|archive-url=https://web.archive.org/web/20200815040340/http://planet4589.org/space/lvdb/list2.html|url-status=dead}} and placed USA-145 into a transfer orbit. The satellite raised itself into medium Earth orbit using a Star-37FM apogee motor.{{cite web|url=http://space.skyrocket.de/doc_sdat/navstar-2r.htm|title=GPS-2R (Navstar-2R)|first=Gunter|last=Krebs|work=Gunter's Space Page|access-date=11 July 2012}}

By 10 November 1999, USA-145 was in an orbit with a perigee of {{convert|20096|km|sp=us}}, an apogee of {{convert|20267|km|sp=us}}, a period of 717.96 minutes, and 53 degrees of inclination to the equator.{{cite web|url=http://planet4589.org/space/log/satcat.txt|title=Satellite Catalog|publisher=Jonathan's Space Page|first=Jonathan|last=McDowell|access-date=11 July 2012}} It is used to broadcast the PRN 11 signal, and operated in slot 2 of plane D of the GPS constellation;{{cite web|url=http://www.astronautix.com/project/navstar.htm|archive-url=https://web.archive.org/web/20021111162023/http://www.astronautix.com/project/navstar.htm|url-status=dead|archive-date=November 11, 2002|title=Navstar|publisher=Encyclopedia Astronautica|first=Mark|last=Wade|access-date=11 July 2012}} however, it had been moved to slot 5 by 2011, with USA-71 covering slot 2. The satellite has a mass of {{convert|2032|kg}}, and a design life of 10 years. As of 2019 it remains in service.

GPS IIR-3 was originally intended to use satellite SVN-50; however, it was damaged during launch preparations in May 1999 after rainwater leaked into the cleanroom atop SLC-17A where the satellite was being attached to its rocket. SVN-50 was repaired and launched as GPS IIR-21, becoming the last IIR to fly.