ESSA-3
{{Short description|Decommissioned American weather satellite}}
{{Use mdy dates|date=October 2018}}
{{Infobox spaceflight
| name = ESSA 3
| names_list = TOS-A
| image = ESSA 3 (cropped).jpg
| image_caption =
| insignia =
| mission_type = Weather satellite
| COSPAR_ID = 1966-087A
| SATCAT = 2435
| mission_duration =
| spacecraft_type =
| spacecraft_bus =
| manufacturer = RCA Astro
| dry_mass =
| launch_mass = {{convert|145|kg}}{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-087A|title=ESSA 3|publisher=National Space Science Data Center|access-date=June 4, 2018}}
| dimensions =
| power =
| launch_date = {{start date text|October 2, 1966, 10:34|timezone=yes}} UTC{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|first=Jonathan|last=McDowell|work=Jonathan's Space Page|access-date=June 4, 2018}}
| launch_rocket = Delta C
| launch_site = Vandenberg LC-2E
| launch_contractor =
| disposal_type = Decommissioned
| deactivated = {{end date text|December 2, 1968}}
| decay_date =
| orbit_epoch = October 2, 1966
| orbit_reference = Geocentric
| orbit_regime = Low Earth
| orbit_periapsis = {{convert|1,383|km|mi|sp=us}}
| orbit_apoapsis = {{convert|1,493|km|mi|sp=us}}
| orbit_inclination = 100.9°
| orbit_semimajor =
| orbit_eccentricity = 0.00703
| orbit_period = 114.6 minutes
| apsis = gee
| programme = TOS
| previous_mission = ESSA-2
| next_mission = ESSA-4
}}
ESSA 3 (or TOS-A) was a spin-stabilized operational meteorological satellite. Its name was derived from that of its oversight agency, the Environmental Science Services Administration (ESSA).
Operation
The satellite's skeleton was made of aluminum and stainless steel and had the shape of a prism with an eighteen-sided base.
Power was supplied by 12,000 1x2 cm photovoltaic cells arranged on its sides, which were used to charge 21 NiCd batteries.
Stabilization in orbit was provided by rotational movement at a speed of 9.2 revolutions per minute, maintained by a magnetic attitude control system (MASC, Magnetic Attitude Spin Coil). Its actuator was a coil, and the torque necessary for position control was generated by the interaction of the Earth's magnetic field with the magnetic field induced in the satellite. An additional stabilization system was provided by five constant-current engines mounted on the circumference of its bottom.{{Cite web |title=ESSA 3 |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-087A |website=NSSDCA}}
A single monopole antenna placed at top was used for communication with Earth. Two dipole antennas (4 rods protruding from the bottom) were used to transmit telemetry.
Cameras were triggered automatically when Earth entered the field of view. The pictures were transmitted directly to Earth or recorded onboard. The satellite was equipped with two twin independent wide-angle Vidicon television cameras. These could work simultaneously or alternately.
The satellite was also equipped with a Flat Plane Radiometer (FPR) used to measure solar energy reflected from the Earth.{{Cite web |title=TIROS 9 / ESSA 1, ..., 9 (Operational TIROS) |url=https://space.skyrocket.de/doc_sdat/essa.htm |access-date=2024-11-05 |website=Gunter's Space Page |language=en}}
Mission
File:Thor Delta E (1966 87).jpg
File:Hurricane Inez in GOM.png
ESSA-3 was launched on October 2, 1966, at 10:34 UTC. It was launched atop a Delta rocket from Vandenberg Air Force Base, California.{{Cite web |title=Launch/Orbital information for ESSA 3 |url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/displayTrajectory.action?id=1966-087A |website=NSSDCA}}{{Cite web |last=McDowell |first=Jonathan |title=launchlog |url=https://planet4589.org/space/gcat/data/derived/launchlog.html |website=Jonathan's Space Report}} The spacecraft had a mass of {{convert|132|kg|lb}} at the time of launch. ESSA-3 had an inclination of 100.9°, and an orbited the Earth once every 114 minutes. Its perigee was {{convert|1383|km|mi|sp=us}} and its apogee was {{convert|1493|km|mi|sp=us}}.{{Cite web |title=Technical details for satellite ESSA 3 (TOS-A) |url=https://www.n2yo.com/satellite/?s=2435 |access-date=2024-11-05 |website=N2YO.com - Real Time Satellite Tracking and Predictions}}
One of the first images taken by ESSA 3 was of Category 4 Hurricane Inez over the Bahamas and Florida.
The satellite operated without failures until January 20, 1967, when its FPR radiometer stopped working. On September 29, 1967, one of the cameras stopped working. On October 9, 1968, the second camera failed. The satellite was decommissioned on December 2, 1968.
References
{{Portal|Spaceflight}}
{{reflist}}
{{NASA|article=ESSA 3|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1966-087A|access-date=June 4, 2018}}
{{TIROS}}
{{Orbital launches in 1966}}
{{DEFAULTSORT:Essa-3}}
Category:Spacecraft launched in 1966