GOES 15

EWS-G2
	The GOES-15 satellite during pre-launch processing.
Names	GOES-P; GOES-15 (before September 22, 2023)
Mission type	Weather satellite
Operator	NOAA / NASA
COSPAR ID	2010-008A
SATCAT no.	36411
Mission duration	10 years (planned); Elapsed: 14 years, 3 months, 11 days
Spacecraft properties
Spacecraft type	GOES-N series
Bus	BSS-601
Manufacturer	Boeing; ITT Corporation
Power	2.3 kilowatts from solar array
Start of mission
Launch date	4 March 2010, 23:57 UTC
Rocket	Delta IV-M+(4,2)
Launch site	Cape Canaveral, SLC-37B
Contractor	United Launch Alliance
Orbital parameters
Reference system	Geocentric
Regime	Geostationary
Longitude	128° West
Slot	GOES-West
Semi-major axis	42,166 kilometres (26,201 mi)
Perigee altitude	35,791.0 kilometres (22,239.5 mi)
Apogee altitude	35,800.4 kilometres (22,245.3 mi)
Inclination	0.2°
Period	1,436.2 minutes

EWS-G2 (Electro-optical Infrared Weather System Geostationary)^[1] is a weather satellite of the U.S. Space Force, formerly GOES-15 (also known as GOES-P before becoming operational). The spacecraft was constructed by Boeing, and is the last of three GOES satellites to be based on the BSS-601 bus. It was launched in 2010, while the other BSS-601 GOES satellites—GOES-13 and GOES-14—were launched in May 2006 and June 2009 respectively.^[2] It was the sixteenth GOES satellite to be launched.

Launch

GOES-15 was launched atop a Delta IV-M+(4,2) rocket flying from Space Launch Complex 37B at the Cape Canaveral Air Force Station.^[3]^[4] The launch occurred at 23:57 UTC on 4 March 2010, forty minutes into a sixty-minute launch window. Upon reaching geostationary orbit on 16 March, it was redesignated GOES-15.^[4]^[5] On 6 December 2011, it was activated as the GOES-West satellite, replacing GOES-11.^[6]

Design

At launch, the mass of the satellite was 3,238 kilograms (7,139 lb). It has a design life of ten years. Power is supplied by a single gallium arsenide solar panel, which provides up to 2.3 kilowatts of power. A 24 cell nickel hydrogen battery is used to provide power when the satellite is not in sunlight.^[7] Instruments aboard GOES-15 include a five channel multispectral imager to capture visible light and infrared images of the continental United States, a sounder to take readings of atmospheric temperature and moisture, a solar x-ray imager to detect solar flares, and instruments to monitor the magnetosphere, cosmic background radiation and charged particles.^[7]

Operations

NOAA began to transition GOES-15 out of operational status at the GOES-West position in late 2018 to replace it with GOES-17.^[8]^[9] GOES-15 began an eastward drift maneuver on 29 October 2018 to 128° W, with all of its sensors still functioning.^[9] GOES-15's drift is intended to provide additional separation from GOES-17 to prevent communication interference. GOES-15 drifted east at a rate of 0.88° per day until 7 November 2018, when it reached its new operating location of 128° West. Once GOES-17 reached its assigned longitude on 13 November 2018, additional tests were performed; provided that testing goes well, GOES-17 will become operational as GOES-West on 10 December 2018.^[9] Both GOES-17 and GOES-15 operated in tandem through early 2020 to allow for assessment of the performance of GOES-17 as the GOES-West operational satellite.^[9] On March 2, 2020, GOES-15 was deactivated and moved to a storage orbit, with plans to re-activate it in August 2020 to back up GOES-17 operations due to a known flaw causing many sensors to become unreliable at night during certain times of the year.^[10]^[11] On 22 September 2023 the satellite's ownership was officially transferred to the U.S. Space Force, taking its current designation as part of the EWS-G network. As a consequence, the spacecraft has started drifting over the Indian Ocean to reach its new assigned orbit and it's scheduled to become operational in November 2023.^[1]