View source for STEX

{{Use dmy dates|date=May 2022}}
{{Infobox spaceflight
| name                  = Science Technology Experiments
| names_list            = STEX<br/>USA 140<br/>NROL-8

<!--image of the spacecraft/mission-->
| image                 = [[File:STEX.jpg|300px]]
| image_caption         = STEX during ground-testing
| image_alt             = <!--image alt text-->
| image_size            =

<!--Basic details-->
| mission_type          = Technology demonstration
| operator              = [[National Reconnaissance Office|NRO]]
| Harvard_designation   = <!--spacecraft launched 1962 and earlier only (eg. 1957 Alpha 2)-->
| COSPAR_ID             = 1998-055A
| SATCAT                = 25489
| website               = <!--Homepage of the craft/mission, OFFICIAL PAGES ONLY-->
| mission_duration      = <!--How long the mission lasted-->
| distance_travelled    = <!--How far the spacecraft travelled (if known)-->
| orbits_completed      = <!--number of times the spacecraft orbited the Earth - see below for spacecraft beyond Earth orbit-->
| suborbital_range      = <!--downrange distance reached if spacecraft did not enter orbit-->
| suborbital_apogee     = <!--altitude reached if spacecraft did not enter orbit-->

<!--Spacecraft properties-->
| spacecraft            = <!--Spacecraft name/serial number (eg. Space Shuttle ''Discovery'', Apollo CM-118), etc-->
| spacecraft_type       = <!--eg. GPS Block II, Kobalt-M, US-K, etc-->
| spacecraft_bus        = <!--eg. A2100M, Star-2, etc-->
| manufacturer          = [[Lockheed Martin]]
| launch_mass           = {{Convert|539.4|kg|abbr=on}}
| BOL_mass              = <!--spacecraft mass in orbit at beginning of operational life, after LEOP phase-->
| landing_mass          = <!--Mass after landing (recovered spacecraft only)-->
| dry_mass              = <!--spacecraft mass in orbit without fuel-->
| payload_mass          = <!--Mass of cargo carried by spacecraft (eg. for Space Shuttle), or total mass of instrumentation/equipment/experiments for mission-->
| dimensions            = <!--body dimensions and solar array span-->
| power                 = <!--end-of-life power, in watts-->

<!--Launch details-->
| launch_date           = {{start date|1998|10|03|10|04|49|7=Z}}
| launch_rocket         = [[Taurus (rocket)]]
| launch_site           = [[Vandenberg AFB]]
| launch_contractor     = <!--organisation(s) that conducted the launch (eg. United Launch Alliance, Arianespace, etc)-->
| deployment_from       = <!--place where deployed from-->
| deployment_date       = <!--date deployed-->
| entered_service       = <!--date on which the spacecraft entered service, if it did not do so immediately after launch-->
<!-- * - e.g. Proton-M/Briz-M not Proton-M, but Titan IV(401)A not Titan IV(401)A-Centaur-->

<!--end of mission-->
| disposal_type         = <!--Whether the spacecraft was deorbited, decommissioned, placed in a graveyard orbit, etc-->
| deactivated           = <!--when craft was decommissioned-->
| destroyed             = <!--when craft was destroyed (if other than by re-entry)-->
| last_contact          = <!--when last signal received if not decommissioned-->
| recovery_by           = <!--recovered by-->
| recovery_date         = <!--recovery date-->
| decay_date            = <!--when craft re-entered the atmosphere, not needed if it landed-->
| landing_date          = <!--when the spacecraft made a controlled landing, not needed if it did not return intact-->
| landing_site          = <!--where the craft landed; site/runway or coordinates-->
<!--
    The following template should be used for ONE of the three above fields "end_of_mission", "decay" or "landing" if the spacecraft is no longer operational.
    If it landed intact, use it for the landing time, otherwise for the date it ceased operations, or the decay date if it was still operational when it re-entered.
    {{end date|YYYY|MM|DD|hh|mm|ss|TZ=Z}} (for Zulu/UTC) or {{end date|YYYY|MM|DD}} (if time unknown)
-->

<!--orbit parameters-->
<!--as science-related articles, SI units should be the principal units of measurement, however we usually use {{convert}} to display imperial units in parentheses after the initial values-->
| orbit_reference       = <!--geocentric, selenocentric, etc - please link (e.g. [[Geocentric orbit|Geocentric]])-->
| orbit_regime          = <!--high, low, medium, molniya, GSO - please link (e.g. [[Low Earth orbit|Low Earth]] - please don't use acronyms-->
| orbit_longitude       = <!--geosynchronous satellites only-->
| orbit_slot            = <!--Designation of orbital position or slot, if not longitude (e.g plane and position of a GPS satellite)-->
| orbit_semimajor       = <!--semimajor axis-->
| orbit_eccentricity    = <!--orbital eccentricity-->
| orbit_periapsis       = <!--periapsis altitude-->
| orbit_apoapsis        = <!--apoapsis altitude-->
| orbit_inclination     = <!--orbital inclination-->
| orbit_period          = <!--time taken to complete an orbit-->
| orbit_RAAN            = <!--right ascension of the ascending node-->
| orbit_arg_periapsis   = <!--argument of perigee/periapsis-->
| orbit_mean_anomaly    = <!--mean anomaly at epoch, only use in conjunction with an epoch value-->
| orbit_mean_motion     = <!--mean motion of the satellite, usually measured in orbits per day-->
| orbit_repeat          = <!--repeat interval/revisit time-->
| orbit_velocity        = <!--speed at which the spacecraft was travelling at epoch - only use for spacecraft with low orbital eccentricity-->
| orbit_epoch           = <!--the date at which the orbit parameters were correct-->
| orbit_rev_number      = <!--revolution number-->
| apsis                 = <!--planet specific apsis term (eg. gee/helion/selene/etc - defaults to generic "apsis")-->

<!--transponder parameters-->
| trans_band            = <!--Transponder frequency bands-->
| trans_frequency       = <!--specific frequencies-->
| trans_bandwidth       = <!--bandwidth-->
| trans_capacity        = <!--capacity of the transponders-->
| trans_coverage        = <!--area covered-->
| trans_TWTA            = <!--TWTA output power-->
| trans_EIRP            = <!--equivalent isotropic power-->
| trans_HPBW            = <!--half-power beam width-->

<!--mission insignia or patch-->
| insignia              = <!--omit the "file" prefix-->
| insignia_caption      = <!--image caption-->
| insignia_alt          = <!--image alt text-->
| insignia_size         = <!--include px/em; defaults to 180px-->
}}

'''Space Technology Experiments''', or '''STEX''', also known as '''NRO Launch 8''' or '''NROL-8''', was an experimental [[National Reconnaissance Office|National Reconnaissance Office (NRO)]] [[satellite]] built by [[Lockheed Martin]]. It was launched on 3 October 1998.<ref name="NSSDC1998-055A">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1998-055A |title=STEX |publisher=NSSDC Master Catalog Search |date=8 October 2010}}</ref> One of the experiments was ATEx (Advanced Tether Experiment), which was deployed on 22 January 1999, and subsequently jettisoned.<ref name="NSSDC1998-055C">{{cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1998-055C |title=ATEx |publisher=NSSDC Master Catalog Search |date=8 October 2010}}</ref>

==ATEx==

[[File:Atex.jpg|thumb|80px|right|Advanced Tether Experiment (ATEx) with partially deployed upper end-body]]

The Advanced Tether Experiment (ATEx), was a follow on to the TiPS experiment, designed and built by the Naval Center for Space Technology, flown as one of the experiments on STEX. ATEx had two end masses connected by a [[polyethylene]] tether that was intended to deploy to a length of 6&nbsp;km, and was intended to test a new [[space tether]] deployment scheme, new tether material, active control, and survivability. ATEx was deployed on 16 January 1999 and ended 18 minutes later after deploying only 22 m of tether. The jettison was triggered by an automatic protection system designed to save STEX if the tether began to stray from its expected departure angle,<ref>{{cite web |agency=U. S. Naval Research Laboratory |url=https://www.nrl.navy.mil/ssdd/programs/atex/ |title=Advanced Tether Experiment (ATEx) |url-status=live |archive-url=https://web.archive.org/web/20150906141352/http://www.nrl.navy.mil/ssdd/programs/atex |archive-date=6 September 2015 }}</ref> which was ultimately caused by excessive slack tether.<ref>{{cite journal |url=https://arc.aiaa.org/doi/abs/10.2514/2.3655 |doi=10.2514/2.3655 |title=Advanced Tether Experiment Deployment Failure |journal=Journal of Spacecraft and Rockets |volume=38 |issue=1 |date=January–February 2001 |pages=60{{hyphen}}68 |last1=Gates |first1=Stephen S. |last2=Koss |first2=Stephen M. |last3=Zedd |first3=Michael F. |bibcode=2001JSpRo..38...60G |url-access=subscription }}</ref> As a result of the deployment failure, none of the desired ATEx goals were achieved.<ref>{{cite web |last=Kramer |first=Herbert J. |url=https://directory.eoportal.org/web/eoportal/satellite-missions/s/stex |title=STEX (Space Technology Experiment) / ATEx |website=eoPortal |publisher=European Space Agency |access-date=18 January 2022}}</ref> ATEx is now tracked as a separate object as USA 141 or [[International Designator|COSPAR ID]] 1998-055C.<ref>{{cite web |title=NSSDCA – STEX – Details |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1998-055A|website=nssdc.gsfc.nasa.gov |agency=[[NASA]] |accessdate=23 June 2016}}</ref>

==References==
{{Reflist}}

==External links==
{{Portal|Spaceflight}}
* [http://space.skyrocket.de/doc_sdat/stex.htm STEX] at Gunter's Space Page

{{Template:National Reconnaissance Office}}
{{NRO Launches}}
{{NRO satellites}}
{{Orbital launches in 1998}}

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[[Category:Spacecraft launched in 1998]]
[[Category:Satellites of the United States]]


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