Seasat

{{Infobox spaceflight

| name = Seasat

| image = Seasat.jpg

| image_caption = Seasat

| mission_type = Oceanography

| operator = NASA / JPL / Caltech

| COSPAR_ID = 1978-064A

| SATCAT = 10967

| mission_duration = Operational:
{{time interval|27 June 1978 01:12|10 October 1978|duration=on}}

| spacecraft_bus = Agena-D

| manufacturer = Lockheed
Ball Aerospace
JPL

| dry_mass =

| launch_mass = {{convert|2290|kg|lb|abbr=on}}{{cite web |url=https://www.wmo-sat.info/oscar/satellites/view/394 |title=Satellite:SeaSat |work=Observing Systems Capability Analysis and Review Tool |publisher=World Meteorological Organization |date=29 July 2015 |access-date=3 June 2019}}

| power = 700 watts

| launch_date = {{start-date|27 June 1978, 01:12}} UTC

| launch_rocket = Atlas E/F Agena-D

| launch_site = Vandenberg SLC-3W

| launch_contractor =

| last_contact = {{end-date|10 October 1978}} UTC

| orbit_epoch = 26 June 1978, 21:12:00 UTC{{Cite web |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1978-064A |title=Spacecraft - Telemetry Details |work=NASA Space Science Data Coordinated Archive |access-date=30 April 2018}}

| orbit_reference = Geocentric

| orbit_regime = Sun-synchronous

| orbit_periapsis = {{convert|769|km|mi|sp=us}}

| orbit_apoapsis = {{convert|799|km|mi|sp=us}}

| orbit_inclination = 108.0 degrees

| orbit_eccentricity = 0.00209

| orbit_period = 100.7 minutes

| apsis = gee

| instruments = {{Infobox spaceflight/Instruments

|acronym1=ALT |name1=Radar Altimeter

|acronym2=LRR |name2=Laser Retro-Reflector

|acronym3=SAR |name3=Synthetic Aperture Radar

|acronym4=SASS |name4=SeaSat-A Scatterometer System

|acronym5=SMMR |name5=Scanning Multichannel Microwave Radiometer

|acronym6=VIRR |name6=Visible and Infrared Radiometer

}}

Seasat{{cite web |url=http://www.jpl.nasa.gov/missions/seasat/ |title=Seasat: Mission Summary |publisher=NASA Jet Propulsion Laboratory |access-date=28 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20140720155023/http://www.jpl.nasa.gov/missions/seasat/ |archive-date=20 July 2014}} was the first Earth-orbiting satellite designed for remote sensing of the Earth's oceans and had on board one of the first spaceborne synthetic-aperture radar (SAR). The mission was designed to demonstrate the feasibility of global satellite monitoring of oceanographic phenomena and to help determine the requirements for an operational ocean remote sensing satellite system. Specific objectives were to collect data on sea-surface winds, sea-surface temperatures, wave heights, internal waves, atmospheric water, sea ice features and ocean topography. Seasat was managed by NASA's Jet Propulsion Laboratory and was launched on 27 June 1978 into a nearly circular {{convert|800|km|mi|abbr=on}} orbit with an inclination of 108°. Seasat operated until 10 October 1978 (UTC), when a massive short circuit in the Agena-D bus electrical system ended the mission.{{cite journal |url=https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19930015504.pdf |title=Report of the Seasat Failure Review Board |journal=Readings in Systems Engineering |publisher=NASA Scientific and Technical Information Program |pages=201–215 |date=1993 |id=NASA-SP-6102; N93-24678 |bibcode=1993rse..nasa..201.}}

Instruments

Seasat carried five major instruments designed to return the maximum information from ocean surfaces:

Radar altimeter to measure spacecraft height above the ocean surface
Microwave scatterometer to measure wind speed and direction
Scanning multichannel microwave radiometer to measure sea surface temperature
Visible and infrared radiometer to identify cloud, land and water features
Synthetic aperture radar (SAR) L-band, HH polarization, fixed look angle to monitor the global surface wave field and polar sea ice conditions {the antenna is the light parallelogram in the picture}. The SAR support structure was designed and manufactured by Northrop Grumman Astro Aerospace in Carpinteria, California. The structure deployed on orbit.

Many later remote sensing missions benefited from Seasat's legacy. These include imaging radars flown on NASA's Space Shuttle, altimeters on Earth-orbiting satellites such as TOPEX/Poseidon, and scatterometers on ADEOS I, QuikSCAT, and Jason-1.

2013 data release

On the 35th anniversary of Seasat's launch, the Alaska Satellite Facility released newly digitized Seasat synthetic aperture radar (SAR) imagery.{{cite web |url=http://www.jpl.nasa.gov/news/news.php?release=2013-208 |title=Trailblazer Sea Satellite Marks Its Coral Anniversary |publisher=NASA Jet Propulsion Laboratory |first=Alan |last=Buis |date=27 June 2013 |access-date=28 June 2013}} Until this release, Seasat SAR data were archived on magnetic tapes, and images processed from the tapes were available only as optical images of film strips or scanned digital images. Neither the tapes nor the film allow the quantitative analysis possible with the new digital archive.{{cite news |url=http://www.adn.com/2013/06/22/2947411/molly-rettig-old-satellite-imagery.html |title=Old satellite imagery offers new baseline data |newspaper=Anchorage Daily News |last=Rettig |first=Molly |date=22 June 2013 |archive-url=https://archive.today/20130629093718/http://www.adn.com/2013/06/22/2947411/molly-rettig-old-satellite-imagery.html |archive-date=29 June 2013 |url-status=dead}}{{cite web |url=https://www-prod.asf.alaska.edu/seasat/ |title=Alaska Satellite Facility Celebrates Seasat 35th Anniversary |publisher=University of Alaska Fairbanks |access-date=28 June 2013 |url-status=dead |archive-url=https://web.archive.org/web/20130708151410/https://www-prod.asf.alaska.edu/seasat/ |archive-date=8 July 2013}}

Conspiracy theory

Seasat is claimed to have been able to detect the wakes of submerged submarines. This supposed capability was unexpected.{{cite news |url=https://www.nytimes.com/1999/05/11/world/us-loses-hold-on-submarine-exposing-radar-technique.html |title=U.S. Loses Hold on Submarine-Exposing Radar Technique |work=The New York Times |first=William J. |last=Broad |date=11 May 1999 |access-date=3 June 2019}} The conspiracy theory holds that when this capability was discovered, the mission was ended for national security reasons, and the end of the mission was falsely blamed on catastrophic failure of the satellite's electric power system.{{cite book |title=Spies in the Sky: Surveillance Satellites in War and Peace |url=https://archive.org/details/spiesskysurveill00norr |url-access=limited |first=Pat |last=Norris |publisher=Praxis |year=2008 |page=[https://archive.org/details/spiesskysurveill00norr/page/n179 172] |isbn=978-0-387-71672-5 |doi=10.1007/978-0-387-71673-2|series=Springer Praxis Books }}{{cite web |url=http://www.shipmodels.info/mws_forum/viewtopic.php?f=14&t=30745 |title=Submarine detection from space |publisher=The Ship Model Forum |access-date=18 November 2008}} Subsequent ocean-observing SAR satellites with higher resolutions and sensitivities have not exhibited this claimed capability.

References

External links

[https://web.archive.org/web/20090704152112/http://www.jpl.nasa.gov/missions/missiondetails.cfm?mission=Seasat JPL Seasat webpage] by the Jet Propulsion Laboratory
[https://www-prod.asf.alaska.edu/seasat/ Seasat portal] {{Webarchive|url=https://web.archive.org/web/20130708151410/https://www-prod.asf.alaska.edu/seasat/ |date=2013-07-08 }} by the Alaska Satellite Facility

Category:Earth observation satellites of the United States

Category:Synthetic aperture radar satellites

Category:Spacecraft launched in 1978

Category:Spacecraft launched by Atlas-Agena rockets

Category:NASA satellites orbiting Earth

Category:Earth satellite radar altimeters