{{Short description|British experimental satellite}} {{Use British English|date=March 2015}} {{Use dmy dates|date=March 2015}} {{Infobox spaceflight | name = Orba | image = | image_caption =

| mission_type = Atmospheric | operator = RAE | website = | mission_duration = Failed to orbit

| spacecraft_bus = | manufacturer = | dry_mass = | launch_mass = | power =

| launch_date = {{start-date|2 September 1970, 00:34:05|timezone=yes}} UTC | launch_rocket = Black Arrow R2 | launch_site = Woomera LA-5B | launch_contractor =

| orbit_epoch = Planned | orbit_reference = Geocentric | orbit_regime = Low Earth | orbit_periapsis = | orbit_apoapsis = | orbit_inclination = | orbit_period = | apsis = gee }}

'''Orba''', also known as '''X-2''', was intended to be the first satellite launched by a British rocket. It was launched at 00:34 GMT on 2 September 1970, atop a Black Arrow rocket from Launch Area 5B at Woomera, but failed to reach orbit after the second stage of the carrier rocket shut down 13 seconds early.<ref name="EA-BA">{{cite web|url=http://www.astronautix.com/lvs/blaarrow.htm|title=Black Arrow|last=Wade|first=Mark|publisher=Encyclopedia Astronautica|access-date=2008-10-28|url-status=dead|archive-url=https://web.archive.org/web/20071206111804/http://www.astronautix.com/lvs/blaarrow.htm|archive-date=6 December 2007|df=dmy-all}}</ref> Orba was built from spare parts due to funding restrictions,<ref name="VE-BA">{{cite web|url=http://www.spaceuk.org/ba/ba.htm|archive-url=https://web.archive.org/web/20030324092948/http://www.spaceuk.org/ba/ba.htm|url-status=usurped|archive-date=24 March 2003|title=Black Arrow|last=Hill|first=Nicholas|work=A Vertical Empire|publisher=Space UK|access-date=2008-10-28}}</ref> and was to have been used to measure upper atmosphere density by monitoring the decay of its orbit.<ref name="GSP">{{cite web|url=https://space.skyrocket.de/doc_sdat/orba.htm|title=Orba (X 2)|last=Krebs|first=Gunter|publisher=Gunter's Space Page|access-date=2008-10-28}}</ref>

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==See also== {{Portal|Spaceflight}} *Prospero X-3 *Timeline of artificial satellites and space probes

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==References== {{reflist}}

{{Black Arrow}} {{Orbital launches in 1970}}

Category:Satellite launch failures Category:Space programme of the United Kingdom Category:Spacecraft launched by Black Arrow rockets Category:Spacecraft launched in 1970 Category:20th-century rocket launches

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