View source for USA-87

{{Short description|American navigation satellite used for GPS}}
{{about|the satellite|the boat|USA 87 (America's Cup Class)}}
{{Use American English|date=December 2020}}
{{use dmy dates|date=December 2020}}
{{Infobox spaceflight
| name              = USA-87
| names_list        = Navstar 2A-08<br/>GPS IIA-8<br/>GPS II-17<br/>GPS SVN-29
| image             = 
| image_caption     = 
| image_size        = 290px

| mission_type      = [[Navigation satellite|Navigation]]
| operator          = [[United States Air Force|U.S. Air Force]]
| COSPAR_ID         = 1992-089A <ref name="Display"/>
| SATCAT            = 22275
| mission_duration  = 7.5 years (planned)<br/>14.75 years (achieved)

| spacecraft        = [[GPS satellite blocks|GPS IIA]]
| spacecraft_type   = [[GPS satellite blocks|GPS Block IIA]]<ref name="GSP"/>
| manufacturer      = [[Rockwell International]]
| launch_mass       = {{cvt|840|kg}}
| dimensions        = {{cvt|5.3|m}} of long
| power             = 710 watts

| launch_date       = 18 December 1992,<br/>22:16:00 [[Coordinated Universal Time|UTC]]
| launch_rocket     = [[Delta II]] 7925-9.5<br/>(Delta D217)
| launch_site       = [[Cape Canaveral Space Force Station|Cape Canaveral]], [[Cape Canaveral Space Launch Complex 17|LC-17B]]
| launch_contractor = [[McDonnell Douglas]]

| entered_service   = 25 January 1993
| disposal_type     = [[Graveyard orbit]]
| deactivated       = 23 October 2007

| orbit_reference   = [[Geocentric orbit]]<ref name="Trajectory"/>
| orbit_regime      = [[Medium Earth orbit]]<br/><small>([[Semi-synchronous orbit|Semi-synchronous]])</small>
| orbit_slot        = F5 (slot 5 plane F)
| orbit_periapsis   = {{cvt|20137|km}}
| orbit_apoapsis    = {{cvt|20541|km}}
| orbit_inclination = 54.74°
| orbit_period      = 720.00 minutes
| apsis             = gee

| programme         = [[Global Positioning System]]
| previous_mission  = [[USA-85]] (GPS IIA-7)
| next_mission      = [[USA-88]] (GPS IIA-9)
}}

'''USA-87''', also known as '''GPS IIA-8''', '''GPS II-17''' and '''GPS SVN-29''', was an American [[navigation satellite]] which formed part of the [[Global Positioning System]]. It was the eighth of nineteen [[GPS satellite blocks|Block IIA]] GPS satellites to be launched.

== Background ==
Global Positioning System (GPS) was developed by the [[United States Department of Defense|U.S. Department of Defense]] to provide all-weather round-the-clock navigation capabilities for military ground, sea, and air forces. Since its implementation, GPS has also become an integral asset in numerous civilian applications and industries around the globe, including recreational used (e.g., boating, aircraft, hiking), corporate vehicle fleet tracking, and surveying. GPS employs 24 spacecraft in 20,200&nbsp;km circular orbits inclined at 55.0°. These vehicles are placed in 6 orbit planes with four operational satellites in each plane.<ref name="Display">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1992-089A|title=Display: Navstar 2A-08 1992-089A|publisher=NASA|date=14 May 2020|access-date=19 December 2020}} {{PD-notice}}</ref>

GPS Block 2 was the operational system, following the demonstration system composed of Block 1 (Navstar 1 - 11) spacecraft. These spacecraft were [[Spacecraft attitude control|3-axis stabilized]], [[nadir]] pointing using [[reaction wheel]]s. Dual solar arrays supplied 710 watts of power. They used [[S band|S-band]] (SGLS) communications for control and telemetry and [[Ultra high frequency]] (UHF) cross-link between spacecraft. The payload consisted of two [[L band|L-band]] navigation signals at 1575.42 [[Hertz|MHz]] (L1) and 1227.60&nbsp;MHz (L2). Each spacecraft carried 2 [[rubidium]] and 2 [[Caesium|Cesium]] clocks and nuclear detonation detection sensors. Built by [[Rockwell International|Rockwell Space Systems]] for the U.S. Air force, the spacecraft measured 5.3 m across with solar panels deployed and had a design life of 7.5 years.<ref name="Display"/>

== Launch ==
USA-87 was launched at 22:16:00 UTC on 18 December 1992, atop a [[Delta II]] [[launch vehicle]], flight number D217, flying in the 7925-9.5 configuration.<ref name="LL">{{cite web |url=https://planet4589.org/space/log/launchlog.txt|title=Launch Log|publisher=Jonathan's Space Report|first=Jonathan|last=McDowell|access-date=10 July 2012}}</ref> The launch took place from [[Cape Canaveral Space Launch Complex 17|Launch Complex 17B]] (LC-17B) at the [[Cape Canaveral Space Force Station|Cape Canaveral Air Force Station]] (CCAFS),<ref name="lvdb">{{cite web|url=http://planet4589.org/space/lvdb/list2.html|title=Launch List|publisher=Jonathan's Space Report|work=Launch Vehicle Database|first=Jonathan|last=McDowell|access-date=10 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}}</ref> and placed USA-87 into a transfer orbit. The satellite raised itself into [[medium Earth orbit]] using a [[Star (rocket stage)|Star-37XFP]] [[Apogee kick motor|apogee motor]].<ref name="GSP">{{cite web |url=https://space.skyrocket.de/doc_sdat/navstar-2a.htm|title=GPS-2A (Navstar-2A)|first=Gunter|last=Krebs|publisher=Gunter's Space Page|access-date=10 July 2012}}</ref>

== Mission ==
On 25 January 1993, USA-87 was in an orbit with a [[apsis|perigee]] of {{cvt|20137|km}}, an [[apsis|apogee]] of {{cvt|20541|km}}, a [[orbital period|period]] of 720.00 minutes, and 54.74° of [[Orbital inclination|inclination]] to the [[equator]].<ref name="Trajectory">{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1992-089A|title=Trajectory: Navstar 2A-08 1992-089A |publisher=NASA|date=14 May 2020|access-date=19 December 2020}} {{PD-notice}}</ref> It had PRN 29, and operated in slot 5 of plane F of the GPS constellation.<ref>{{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=11 November 2002|title=Navstar|publisher=Encyclopedia Astronautica|first=Mark|last=Wade|access-date=10 July 2012}}</ref> The satellite had a mass of {{cvt|840|kg}}. It had a design life of 7.5 years,<ref name="GSP"/> and ceased operations on 23 October 2007.

== References ==
{{Portal|Spaceflight}}
{{Reflist|2}}

{{GPS satellites}}
{{Orbital launches in 1992}}

[[Category:Spacecraft launched in 1992]]
[[Category:GPS satellites]]
[[Category:USA satellites]]