ESSA-4
{{Use mdy dates|date=October 2018}}
{{Infobox spaceflight
| name = ESSA 4
| names_list =
| image = ESSA 4 (cropped).jpg
| image_caption =
| image_size =
| mission_type = Weather
| operator = NASA
| COSPAR_ID = 1967-006A
| SATCAT = S02657
| website =
| mission_duration =
| spacecraft =
| spacecraft_type =
| spacecraft_bus =
| manufacturer =
| launch_mass = {{cvt|290|kg}}
| dimensions =
| power =
| launch_date = 21 January 1967, 17:31 GMT
| launch_rocket = Thor-Delta E
| launch_site = Vandenberg Space Launch Complex 2
| launch_contractor =
| entered_service = 21 January 1967
| last_contact =
| deactivated = 5 May 1968
| decay_date =
| orbit_reference = Geocentric orbit
| orbit_regime = Low Earth orbit
| orbit_periapsis = {{cvt|1338|km}}
| orbit_apoapsis = {{cvt|1443|km}}
| orbit_inclination = 102°
| orbit_period = 113.48 minutes
| orbit_eccentricity = 0.00740
| apsis = gee
| instruments =
| programme = ESSA program
| previous_mission = ESSA-3
| next_mission = ESSA-5
}}
ESSA-4 (or TOS-B) was a spin-stabilized operational meteorological satellite. Its name was derived from that of its oversight agency, the Environmental Science Services Administration (ESSA).
Background
ESSA 4 was launched to replace ESSA 2, launched February 3, 1966, which had drifted into an orbit of limited usefulness. The satellite was financed, managed, and operated by the Environmental Science Services Administration (ESSA).{{cite web|title=Aeronautics and Astronautics, 1967|url=https://history.nasa.gov/AAchronologies/1967.pdf|access-date=21 December 2021|publisher=NASA|page=20}}
Spacecraft
Launch
File:Launch of ESSA IV Spac0002-retouched.jpg
ESSA-4 was launched on January 26, 1967, at 17:31 UTC. It was launched atop a Delta rocket from Vandenberg Space Launch Complex 2,{{cite web|url=https://planet4589.org/space/gcat/data/derived/launchlog.html|title=Launch Log|author=Jonathan McDowell|author-link=Jonathan McDowell|access-date=21 December 2021}} into Sun-synchronous orbit. ESSA-4 had an inclination of 102°, and an orbited the Earth once every 113.4 minutes. Its perigee was {{convert|1328|km|mi|sp=us}} and its apogee was {{convert|1443|km|mi|sp=us}}.
The satellite properly aligned itself with respect to the Earth during its 18th orbit, whereupon its first photos were transmitted. A two-week spacecraft checkout and evaluation program ensued. One of the APTs failed after launch, but the other performed normally.{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1967-006A|title=ESSA 4|access-date=21 December 2021}}
Legacy and status
References
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{{Orbital launches in 1967}}
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Category:Spacecraft launched in 1967