An Atlas V rocket has successfully deployed a next-generation weather satellite for the US National Oceanic and Atmospheric Administration on Saturday. The United Launch Alliance (ULA) rocket launched from SLC-41 at Cape Canaveral at the end of a one hour-long window at 18:42 local time (23:42 UTC).
The GOES-R satellite, which rode aboard Saturday’s launch, begins a new fifth generation of geostationary weather satellite for the United States. It is the first of four satellites in its class which are expected to launch over the next eight year period.
GOES-R is part of the Geostationary Operational Environmental Satellite (GOES) program, operated by the National Oceanic and Atmospheric Administration (NOAA).
GOES consists of two operational satellites in geosynchronous orbit over the United States, providing images and data for weather forecasting across the western hemisphere. One satellite is located at a longitude of 75 degrees West – a station designated GOES-EAST – covering the Eastern United States, the Central and West Atlantic, the Gulf of Mexico and the Caribbean.
The second satellite, designated GOES-WEST, is positioned at 137 degrees West and covers the western States – including Alaska and Hawaii – as well as the Eastern and Central Pacific.
At present, the GOES-EAST slot is occupied by GOES 13, while GOES-WEST coverage is provided by GOES 15. These satellites launched in May 2006 and March 2010 as GOES-N and GOES-P respectively. The GOES 14 satellite, formerly GOES-O, has served as an on-orbit spare since its launch in 2009 and has occasionally been called into service to cover outages as GOES 13 begins to show its age.
In addition to weather forecasting, the GOES satellites are used to study space weather phenomena and conduct research into the Earth’s magnetosphere and radiation environment.
Before launch, GOES satellites are designated with a letter to identify their place in the program’s launch order. Upon successfully reaching orbit this is replaced with a sequential number. GOES-R will become GOES 16 after a successful launch, following GOES-P which became GOES 15. Numbers are only given to satellites that launched successfully; GOES-G would have become GOES 7 but was lost in a launch failure, so GOES-H instead became GOES 7 after its launch the following year.
There was no GOES-Q satellite; the designation was assigned to an option in the contract for the GOES-N class satellites, which was not exercised.
The GOES program evolved from the NOAA’s earlier Synchronous Meteorological Satellite (SMS) series, which consisted of two prototype spacecraft launched in May 1974 and February 1975 atop Delta 2914 rockets.
With the success of these missions, the NOAA began the GOES series with three satellites – GOES 1 to 3 – manufactured by Ford and based on the SMS design, launched between October 1975 and June 1978. These early satellites were spin-stabilised with spin-scan radiometers to image the Earth as the satellites spun. After their retirement as weather satellites, GOES 2 and 3 were used as communications satellites over the Pacific Ocean, with GOES 2 operating until 2001.
As its orbital inclination increased naturally over time, GOES 3 became an important communications relay for the Amundsen-Scott research station at the South Pole which does not have a line-of-sight to geostationary satellites. GOES 3 operated in this role until it was decommissioned on 29 June this year, thirty-six years after launch.
The second generation of the GOES constellation consisted of five satellites constructed by Hughes based around the HS-371 bus. These were launched by Delta 3914 rockets between September 1980 and February 1987. Like their predecessors these satellites were spin-stabilised, with an improved imaging payload over the first-generation.
The series initially consisted of four satellites plus a ground spare. The fourth satellite, GOES-G was lost at launch on 3 May 1986, after the Delta rocket’s first stage engine cut out 71 seconds after liftoff. Even before the failure, the ground spare had been called up to launch due to delays with the procurement of the next generation of satellites.
Because of the delays to the third generation – or GOES-I series – satellites and the loss of GOES-G, the retirement of GOES 4 in November 1998 left the NOAA with no spare satellites in orbit. When the imaging payload aboard GOES 6 failed three months later, the agency was left with no satellite to cover the West Coast of the United States. GOES 7 was moved from the Eastern slot to a more central position where it could cover the continental US, and in 1992 NOAA leased Europe’s spare Meteosat-3 satellite, allowing GOES 7 to move further West.
Third-generation satellites finally began to launch in April 1994, with an Atlas I carrying GOES 8 into orbit. Following on-orbit testing it entered service at the GOES-EAST position in 1995, allowing Meteosat-3 to be returned to the European Space Agency for decommissioning and GOES 7 to move west again into the regular GOES-WEST position resuming the constellation’s normal service.
GOES 7 was relieved by GOES 9, which launched in May 1995. Like GOES 2 and 3, GOES 7 was used as a communications satellite over the Pacific following the end of its operational service. It was finally decommissioned in 2012.
GOES 10 was launched as an on-orbit spare in April 1997. A year later it swapped roles with GOES 9 after a fault was identified in the latter’s attitude control system, although GOES 9 would later be leased to the Japan Meteorological Agency to replace its failing Himawari-5 satellite.
Two further third-generation GOES satellites, GOES 11 and 12, were launched in 2000 and 2001 by Atlas IIA rockets. The more powerful rockets allowed the satellites to carry additional fuel, allowing a greater potential for extended operations after the end of their normal service lives. GOES 12 carried an additional space weather instrument, the Solar X-Ray Imager (SXI). The third-generation satellites were built by Space Systems Loral, and were the first GOES spacecraft to be three-axis stabilized.
The contract for two fourth-generation GOES satellites, the GOES-N series, was awarded to Hughes in February 1998 along with options for two further satellites, one of which was exercised. The satellites were manufactured by Boeing following its 2000 purchase of Hughes’ satellite manufacturing division and launched atop Delta IV rockets between 2006 and 2010. The three third-generation satellites, GOES 13, 14 and 15, are now the only operational GOES spacecraft following the decommissioning of GOES 12 in 2013.
GOES-R is the first of four GOES-R-class satellites that form the fifth generation of the GOES constellation. Constructed by Lockheed Martin and based on the A2100A satellite bus, each satellite has a dry mass of 2,857 kilograms (6,299 lb) which increases to 5,192 kilograms (11,466 lb) when fully-fuelled at launch. The spacecraft measure 6.1 by 5.6 by 3.9 meters (20 x 18 x 13 feet) and have fifteen-year design lives; expected to consist of ten years of operational use and up to five years of storage as an on-orbit spare.
GOES-R carries six scientific payloads and a data relay payload. Its nadir-pointing – Earth-facing – instruments are mounted on the side of the satellite which will be pointed towards Earth in orbit. Solar-pointing instruments are located on the arm which holds the satellite’s solar array; to provide power to the spacecraft this arm must track the sun, allowing its instruments to make near-constant observations. Further sensors will allow the satellite to study its surrounding environment.
The primary instrument aboard GOES-R is its Advanced Baseline Imager (ABI), built by Harris Corporation of Florida. Producing images across sixteen spectral bands from visible to infrared, ABI can achieve a spatial resolution of 500 metres (547 yards) at its primary visible-light wavelength of 0.64 nanometres and 2,000 metres (2,187 yards) in the infrared; roughly twice the resolution of the imager aboard the GOES-N series, which only operates in five spectral bands.
The imager can be used to produce full-disc images of the Earth or more targeted regional scans – including of the continental United States or in a mesoscale imaging mode that allows it to image a square box with sides of one thousand kilometers (621.4 miles, 540.0 nautical miles). In normal operation, the spacecraft will take four full-disc images, twelve scans of the continental United States and up to 120 mesoscale images every hour.
Unlike the previous two generations of satellite, GOES-R does not carry an atmospheric sounding payload. One was to have been included as part of the Hyperspectral Environmental Suite (HES), a set of additional instruments which were part of the spacecraft’s original design but were removed in 2006 after proving too complicated to develop. Instead, data which would have been provided by the sounder will be interpolated from ABI’s images.
The Geostationary Lightning Mapper (GLM) is a new instrument for the GOES-R series, a near-infrared sensor designed to detect and capture sudden visual events across the area it is monitoring. GLM will record and map lightning activity over the Americas, the West Atlantic and the Pacific Ocean. GLM is expected to improve forecasters’ ability to predict storms as they develop, giving advance warning of severe weather activity.
The Solar Ultraviolet Imager, or SUVI, is one of two payloads which will study the Sun. It is designed to capture full-disc images in the extreme ultraviolet. SUVI will be used in space weather forecasting, monitoring activity across the face of the sun and eruptions and solar flares. SUVI is the successor to the Solar X-ray Imager (SXI) that was introduced with the GOES 12 satellite.
The second Solar-monitoring payload, the Extreme Ultraviolet and X-Ray Irradiance Sensors, or EXIS, consists of two instruments. Its Extreme Ultraviolet Sensor (EUVS) contains three grating spectrographs which will be used to measure variations in three particular spectral emission lines – from Helium, Hydrogen and Magnesium – in light coming from the Sun.
These lines correspond to emissions from different regions of the Sun and can be used to model the Sun’s entire ultraviolet spectrum. The X-Ray Sensor (XRS) is a successor to an X-ray monitoring payload that has been carried on all GOES satellites since the beginning of the program, which is used to measure solar irradiance and characterize solar flares. XRS uses silicon photodiodes to measure incident radiation within two spectral bands: 0.05 to 0.4 nanometres and 0.1 to 0.8 nanometres.
The Space Environment In-Situ Suite (SEISS) consists of five sensor packages to study and characterize the space environment in which GOES-R will operate. Its Energetic Heavy Ion Sensor (EHIS) will measure the flux of larger energized particles both within the magnetosphere and incident from solar or cosmic sources.
Two Magnetic Particle Sensors, MPS-Hi and MPS-Lo, will measure proton and electron flux; the former monitoring high-energy particles while the latter will study particles at lower energies. Two identical Solar and Galactic Proton Sensor (SGPS) packages complete the suite, measuring the incidence of Protons into Earth’s magnetosphere from the Sun and from cosmic sources.
The final scientific payload, a magnetometer, is mounted at the end of an extendible boom which GOES-R will deploy once in orbit. The magnetometer will be used to characterize activity in the outer region of Earth’s magnetosphere.
In addition to its scientific instruments, GOES-R carries a communications payload which is mounted on the solar array arm alongside the solar research payloads. Unique Payload Services, as this is named, consists of transponders to relay data for the GOES Rebroadcast (GRB), Data Collection System (DCS), Emergency Managers Weather Information Network (EMWIN) and Search and Rescue Satellite Aided Tracking (SARSAT) projects.
GOES Rebroadcast allows anyone with a compatible receiver to downlink observational data directly from the satellite. DCS collects data from unmanned environmental research stations and relays it back to a ground station.
EMWIN is used to make weather forecasting data and warnings available for emergency management, while SARSAT is a worldwide program using satellites in low and geostationary orbits to detect distress signals from land, ships and aircraft and relay them to rescue services.
GOES-R was launched by United Launch Alliance (ULA), using an Atlas V rocket. The vehicle, with the tail number AV-069, flew in the 541 configuration, with a five-metre (16.4-foot) payload fairing, four AJ-60A solid rocket motors augmenting a Common Core Booster first stage, and a single-engine Centaur upper stage.
Saturday’s launch was the sixty-seventh flight of an Atlas V, and the fourth for the Atlas V 541.
The Atlas V was developed by Lockheed Martin under the US Air Force’s Evolved Expendable Launch Vehicle (EELV) program, and first flew in August 2002 deploying Eutelsat’s Hot Bird 6 satellite.
Boeing developed the Delta IV – which has made 33 flights to date – under the same program and Saturday’s launch was the one-hundredth between the two rockets. Since December 2006 both the Atlas V and Delta IV – along with the older Delta II rocket – have been operated by United Launch Alliance, a joint venture between Boeing and Lockheed Martin.
The launch of GOES-R took a little over three and a half hours from liftoff to spacecraft separation, with the satellite expected to be deployed into a geosynchronous transfer orbit with a perigee of 8099 kilometres (5032 miles, 4373 nautical miles), an apogee of 35,286 kilometres (21,926 miles, 19,053 nautical miles) and 10.6 degrees inclination to the equator.
ULA had a one-hour window in which to launch GOES-R on Saturday, which began at 17:42 Eastern Standard Time, or 22:42 UTC. Weather forecasts ahead of the launch were optimistic, with a 10% probability of unacceptable conditions predicted.
However, a technical hold, followed by a Range issue, resulted in the launch moving to the end of the window.
The launch took place from Space Launch Complex 41 (SLC-41) at the Cape Canaveral Air Force Station. A former Titan launch complex which was originally constructed in the 1960s, SLC-41 has been the East Coast home of the Atlas V since it was introduced in 2002.
Atlas vehicles are assembled atop a mobile launch platform in the nearby Vertical Integration Building and rolled to the launch pad shortly ahead of launch. AV-069 was moved to the pad Friday morning.
The Atlas is a two-stage vehicle, consisting of a Common Core Booster (CCB) first stage and a Centaur upper stage. The CCB is powered by a single RD-180 engine, manufactured by NPO Energomash of Russia, which burns RP-1 propellant oxidized by liquid oxygen.
Igniting 2.7 seconds ahead of the planned liftoff, the RD-180 is the rocket’s principal source of thrust during the early stages of flight as Atlas climbs through Earth’s atmosphere. At liftoff, four Aerojet Rocketdyne AJ-60A solid rocket motors (SRMs) will ignite to provide additional thrust.
Following first stage ignition, it took a few seconds for the RD-180 to reach launch thrust. Liftoff occurred at about 1.1 seconds after the zero mark in the countdown, when the force generated by the main engine and solid rocket motors exceeds the weight of the loaded vehicle. AV-069 began her ascent away from Cape Canaveral, beginning a series of pitch and yaw maneuvers 5.2 seconds after launch. The rocket flew along an azimuth of 100.7 degrees, taking it East and slightly South over the Atlantic Ocean.
Thirty-five and a half seconds after liftoff, Atlas’ velocity reached Mach 1, the speed of sound. The rocket experienced maximum dynamic pressure – or Max-Q – 10.7 seconds later as it continued to climb. The SRMs burned out around 85 to 90 seconds into flight and separated in pairs; the first pair detaching at 110.4 seconds after liftoff and the second pair a second and a half later.
At three minutes and 29.9 seconds after launch, the payload fairing separated from around GOES-R at the nose of the rocket. By this stage, Atlas was at an altitude in excess of 100 kilometers (62 miles, 54 nautical miles), above the denser regions of the atmosphere which would damage the spacecraft if it were unprotected. Because the five-metre fairing encapsulates not just the satellite but also the Centaur upper stage, it must be jettisoned before the first stage can separate.
First stage flight ended with Booster Engine Cutoff, or BECO, four minutes and 21.8 seconds after liftoff. The spent stage separated six seconds later. Following staging, the Centaur’s single RL10C-1 engine began a prestart sequence ahead of its ignition ten seconds later.
Powered by the combustion of liquid hydrogen propellant, oxidized by liquid oxygen, the Centaur made three burns during Saturday’s mission. From separation, the first burn lasted seven minutes and 37.8 seconds.
Following a nine-minute, 43-second coast phase, the Centaur restarted for a five-minute, 38-second burn that raised its orbital apogee towards geosynchronous altitude.
Following the burn, Centaur coasted towards its apogee, with its third burn eighteen-tenths of a second short of three hours later. The third and final burn lasted 93.3 seconds, raising the orbit’s perigee and reducing its inclination; decreasing the amount of propellant GOES-R will need to burn to reach its final geostationary station.
Spacecraft separation occurred 69 seconds after the end of the third burn, at three hours, 31 minutes and 54.9 seconds mission elapsed time.
Following separation GOES-R will use its LEROS-1C apogee motor to perform a series of orbit-raising maneuvers. Upon arrival in geostationary orbit, the satellite will undergo around a year of test and checkout operations. It is currently expected to replace GOES 13 in the GOES-EAST slot late next year, with GOES 13 becoming an additional on-orbit spare. GOES-R is designed for up to ten years of operational life plus five years of on-orbit storage; it is currently scheduled to be replaced by GOES-T in late 2025.
Saturday’s launch was the seventh of eight Atlas V missions planned for 2016, coming just eight days after the launch of the WorldView-4 commercial imaging satellite from Vandenberg Air Force Base, a mission which had been delayed from September by brush fires around the launch site. One further launch is planned before the end of the year, which will fly from Cape Canaveral in mid-December with the EchoStar XIX communications satellite.
For United Launch Alliance, who have also conducted three Delta IV launches this year, it was the tenth flight of the year. ULA’s next launch will be on 7 December when the last Delta of the year will carry a Wideband Global Satcom spacecraft into orbit.
The next GOES satellite, GOES-S, is currently scheduled for launch aboard another Atlas V in 2018. Before then, the NOAA’s next low-orbit weather satellite, JPSS-1, is expected to launch atop a Delta II next March.
(Images via NSF member SaxtonHale, ULA, NOAA, Lockheed Martin and NASA).