On Wednesday, China launched a double satellite mission intended for research in electromagnetic counterparts of gravitational waves. The launch took place from the Xichang Satellite Center, Sichuan province, at 20:15 UTC using a Long March-11 – Chang Zheng-11 – launch vehicle.
According to the National Space Science Center under the Chinese Academy of Sciences (CAS), the Gravitational Wave High-energy Electromagnetic Counterpart All-Sky Monitor (GECAM) mission is composed of two small satellites, and it will focus on detecting electromagnetic counterparts of gravitational waves, high-energy radiation from fast radio bursts, various gamma-ray bursts, and magnetar flares.
The mission will help scientists unravel the mysteries of compact objects, such as neutron stars and black holes, as well as the merger of binary compact objects.
In February 2016, the Laser Interferometer Gravitational-Wave Observatory announced the first gravitational waves’ detection. In March of that year, the GECAM mission was proposed by the CAS’s Institute of High Energy Physics in Beijing. The mission’s prototype was funded in July 2016, with the engineering review of the mission taking place in December 2017.
Adopted by CAS in July 2018, the mission is officially funded in December that year with a launch scheduled for the end of 2020 with tight constraints on the budget and technology readiness both for spacecraft and payload.
Also designated KX-08A and KX-08B, each satellite has a launch mass of 150 kg and features a dome-shaped array of 25 Gamma-ray detectors (GRD) and 8 Charged particle detectors (CPD). Together the satellites will provide a FOV of 100% all-sky. The sensitivity of the detectors is ~2E-8 erg/cm2/s. They will provide localization of ~1°. The detectors are sensible in the energy band from 6 keV to 5 MeV.
The GRDs will monitor x/gamma rays from all of the sky, providing information on temporal, spectral, localization measurements for Gamma-ray Bursts.
The CPD will monitor charged particles (both electrons and protons) and identify the GRD bursts produced by charged particles, distinguishing GRB and fake GRB.
The satellites will operate in an orbit at 600 km altitude with an inclination of 29 degrees. The mission will give real-time alerts providing information about the event’s trigger time, localization, duration, spectrum, etc., with latency between 2 to 10 minutes.
The mission will be important for the detection of Gamma-ray emission of Gravitational-Wave sources; for the study of Gamma-ray emission of High Energy Neutrino (HEN) and Gamma-ray emission of Fast Radio Bursts and Gamma-ray Bursts, especially ultra-long and ultra-soft ones; study of Soft Gamma-ray Repeaters SGR/ Anomalous x-ray pulsars (AXP); the study of Tidal Disruption Events (TDE), X-Ray Bursts, long term X-Ray Binaries and X-ray Pulsars; Solar flares; Terrestrial Gamma-ray Flashes and Terrestrial Electron Beams.
This was the eleventh launch of the Long March-11, including the CZ-11H version launched from a maritime launch platform.
The Long March-11 (Chang Zheng-11) is a small solid-fuelled quick-reaction launch vehicle developed by the China Academy of Launch Vehicle Technology (CALT) to provide an easy to operate quick-reaction launch vehicle that can remain in storage for a long period and provide a reliable launch on short notice.
LM-11 is a four-stage solid-fuelled launch vehicle equipped with a reaction control system on the fourth stage.
The vehicle has a length of 20.8 meters, 2.0 meters in diameter, and a lift-off mass of 58,000 kg. At launch, it develops 120.000 kg/f, launching a 350 kg cargo into a 700 km SSO. The CZ-11 can use two types of fairing with 1.6 meters or 2.0 meters.
LM-11’s first launch took place on September 25, 2015, when successfully orbited four satellites from the Jiuquan Satellite Launch Center.
The CZ-11 can also be launched from a maritime launch platform using the CZ-11H version.
The Xichang Satellite Launch Centre is situated in the Sichuan Province, south-western China, and is the country’s launch site for geosynchronous orbital launches.
Equipped with two launch pads (LC2 and LC3) and a launch zone for the launch of solid launch vehicles, the center has a dedicated railway and highway lead directly to the launch site.
The Command and Control Centre is located seven kilometers south-west of the launch pad, providing flight and safety control during launch rehearsal and launch.
Other facilities on the Xichang Satellite Launch Centre are the Launch Control Centre, propellant fuelling systems, communications systems for launch command, telephone and data communications for users, and support equipment for meteorological monitoring and forecasting.