SMILE project satellite expected to be launched in fall 2025, a space mission which aims to measure Earth's global system responses to solar wind and geomagnetic variations.
Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) is a planned joint venture mission between the European Space Agency and the Chinese Academy of Sciences. SMILE will image for the first time the magnetosphere of the Sun in soft X-rays and UV during up to 40 hours per orbit, improving our understanding of the dynamic interaction between the solar wind and Earth's magnetosphere. SMILE will investigate the dynamic response of the Earth's magnetosphere to the impact of the solar wind in a unique manner, never attempted before: it will combine soft X-ray imaging of the Earth's magnetopause and magnetospheric cusps with simultaneous UV imaging of the Northern aurora.
For the first time it will be possible to trace and link the processes of solar wind injection in the magnetosphere with those acting on the charged particles precipitating into the cusps and eventually the aurora. With its unparallelled payload SMILE will provide answers to many of the open questions in solar-terrestrial relationships in a thoroughly novel way.
Scientists and engineers from the UK, China, Canada, several European countries and the US are collaborating in order to make SMILE a reality.
The next SMILE Science Working Team meeting will take place in Akureyri, Iceland 7-10 October 2024.
The prime science questions of the SMILE mission are:
- What are the fundamental modes of the dayside solar wind/magnetosphere interaction?
- What defines the substorm cycle?
- How do coronal mass ejection-driven storms arise and what is their relationship to substorms?
As of April 2024, SMILE is expected to launch in late 2025.
Project History
SMILE was put forward in March 2015 in response to the European Space Agency and Chinese Academy of Sciences joint call for a small-size space mission. The Executive Summary of the submitted proposal can be found here.
SMILE was chosen for an initial study phase during the summer of 2015. An initial study of the whole mission was carried out by ESA and CAS at their Concurrent Design Facilities during October 2015, and the conclusion was that the mission is feasible, with no show stoppers. In early November 2015 SMILE was formally selected by the ESA Science Programme Committee (SPC).
The SMILE Mission System Requirements Review was successfully closed in early October 2018, the SMILE Definition Study Report (the Red Book) was published in December 2018, and Mission Adoption by the ESA SPC was granted in early March 2019. This means that SMILE is now formally part of ESA's Cosmic Vision programme and has received the green light for implementation. Platform and instruments have successfully gone through their Preliminary Design Review (2021) and are now preparing for the Critical Design Review and Flight Model build. As stated above, launch is expected to take place in early 2025.
Project Overview
The mission will observe the solar wind interaction with the magnetosphere with its X-ray and ultraviolet cameras (SXI and UVI), gathering simultaneous images and videos of the dayside magnetopause (where Earth's magnetosphere meets the solar wind), the polar cusps (a region in each hemisphere where particles from the solar wind have direct access to Earth's ionosphere), and the auroral oval (the region around each geomagnetic pole where auroras most often occur). SMILE will also gather simultaneously in situ measurements with its two other instruments making up its payload – an ion analyzer (LIA) and a magnetometer (MAG). These instruments will monitor the ions in the solar wind, magnetosheath and magnetosphere while detecting changes in the local DC magnetic field.
SMILE must reach a high enough altitude to view the outside edge of Earth's magnetopause and at the same time obtain good spatial resolution of the auroral oval. The chosen orbit is therefore highly elliptical and highly inclined (70 or 98 degrees depending on the launcher), and takes SMILE a third of the way to the Moon at apogee (an altitude of 121 182 km, i.e. 19 Earth radii or RE). This type of orbit enables SMILE to spend much of its time (about 80%, equivalent to nine months of the year) at high altitude, allowing the spacecraft to collect continuous observations for the first time during more than 40h. This orbit also limits the time spent in the high-radiation Van Allen belts, and in the two toroidal belts. SMILE will be injected into a low Earth orbit by a Vega-C launch vehicle from Kourou, French Guiana, and its propulsion module will bring the spacecraft to the nominal orbit with perigee altitude of around 5000 km.[1]
The SMILE spacecraft consists of a platform provided by the Chinese Academy of Sciences (CAS) attached to a payload module containing nearly all of the scientific instruments and an X-band communications system, provided by ESA. The payload module will be built by Airbus. The platform is composed of a propulsion and a service module, together with the two detectors (or heads) of the ion instrument. The Mission Operations Center will be run by CAS; both organizations will jointly operate the Science Operations Center.
Instruments
Key instruments on board the spacecraft are developed through international cooperation and will include:
- Soft X-ray Imager (SXI) – wide-field lobster-eye telescope using micropore optics to spectrally map the location, shape, and motion of Earth's magnetospheric boundaries, including the bow shock, magnetopause, and cusps, by observing emission from the [Solar Wind Charge eXchange (SWCX) process. The SXI is equipped with two large X-ray-sensitive Charge-coupled device (CCD) detectors covering the 0.2 keV to 2.5 keV energy band, and has an optic field of view spanning 15.5° × 26.5°. This telescope is being developed, built, and will be calibrated at the University of Leicester, UK, and other institutions throughout Europe. CCDs are being procured from Teledyne e2v, UK, by ESA and calibrated by The Open University, UK.
- UV Imager (UVI) – an ultraviolet camera to image Earth's northern auroral regions. It will study the connection between the processes taking place at the magnetospheric boundaries – as seen by the SXI – and those acting on the charged particles precipitating into our ionosphere. The UVI is a CCD camera centered on the 160-180 nm waveband, with a 10° × 10° field of view. It will have a spatial image resolution at apogee of 150 km, and will use four thin film-coated mirrors to guide light into its detector. Temporal resolution will be up to 60s. UVI is built by NSSC with collaboration from BelgiumLiège Space Center (CSL), ESA, Calgary University and the Polar Research Institute of China.
- Light Ion Analyser (LIA) – will determine the properties and behaviour of the solar wind and magnetosheath ions under various conditions by measuring the three-dimensional velocity distribution of protons and alpha particles. It is made of two top-hat-type electrostatic analysers, each mounted on opposite side of the platform. It is capable of sampling the full 4 π three-dimensional distribution of the solar wind, and can measure ions in the energy range 0.05 to 20 keV at up 0.5 second time resolution. It is a joint venture between the Chinese National Space Science Centre, CAS, and University College London's Mullard Space Science Laboratory (UCL-MSSL), UK and LPP/CNRS/Ecole Polytechnique, France.
- Magnetometer (MAG) – will be used to determine the orientation and magnitude of the magnetic field in the solar wind and magnetosheath, and to detect any solar wind shocks or discontinuities passing over the spacecraft. Two tri-axial sensors will be mounted away from the spacecraft on a 3-m-long boom some 80 cm apart, with a corresponding electronics unit mounted on SMILE's main body. This configuration will let the MAG act as a gradiometer, and allow SMILE's background magnetic field to be accurately determined and subtracted from any measurements. MAG will measure the three components of the magnetic field in the range +/- 12800 nT. It is joint venture between the Chinese National Space Science Centre, CAS, and the Space Research Institute, Austrian Academy of Sciences.
International Project Science Working Groups
A number of SMILE Science Working Groups have been established in order to support the SMILE mission development and operations, ensuring that the science objectives are achieved and optimized, and adding value to SMILE science through the contributions of complementary measurements on the ground and in space.
SWG - Science Operations (Chair: Philippe Escoubet, ESA)
This WG has been established to coordinate the preparations and the smooth running of SMILE's flight operations. Current activities comprise the preparation of the Master Science Plan, the definition of planning/commanding requirements for the spacecraft and the four instruments in the payload, and the interfaces with the ground systems of both CAS and ESA.
SWG - In Situ (Chair: Lei Dai, NSSC/CAS)
The WG activity is centered on optimising the design, operations and calibrations planning of the in situ instrument package. A report reviewing science objectives, pointing and measurement accuracy requirements, operational modes, calibration plans and data products is being prepared.
SWG - Data Formats and Calibration (Chair: Catarina Alves de Oliveira, ESA)
The WG had a kick-off meeting at ESAC, near Madrid, Spain, in January 2018. Studies and discussions are ongoing in order to establish the most effective way to incorporate the remote sensing and in situ data which SMILE will return into a user-friendly framework, taking into account the different formats used. The WG has picked up momentum from the monthly teleconferences where topics such as the science data exchange process, commonly used formats of remote sensing and in situ data, and the conversion between them, archiving and version control, are presented and discussed in view of their eventual implementation. The presentations can be accessed using ESA COSMOS account credentials.
SWG - Ground-Based and Additional Science (GBAS) (Chair: Jenny Carter, Leicester University)
Links with ground observers are already well established (as illustrated in the SMILE ground-based support document by Carter et al. 2015). Preliminary contacts with operational and forthcoming space missions are taking place in order to coordinate observing and software efforts.
SWG - Outreach (Chair: Graziella Branduardi-Raymont, MSSL/UCL)
Much discussion and activity is taking place generating contacts with organisations promoting science in primary and secondary schools, holding workshops and advocating careers in science, focusing on SMILE as a practical example of how space projects are developed, and encouraging pupils to follow its progress to launch and beyond. Many of these public engagement initiatives are similar to those organised in the context of other space missions. A White Paper has been produced which collates the approaches taken in the UK and provides recommendations for best practice. The WG is happy to share presentations on SMILE and outreach material (password protected) and welcomes their use targeted to engage more cohorts of students.
SWG - Modelling (Co-Chairs: Hyunju Connor, GSFC/NASA, Tianran Sun, NSSC/CAS, Andrey Samsonov, MSSL/UCL)
This WG aims to coordinate and drive the simulation and modelling activities ongoing in many SMILE collaborating institutes and leading to predict the soft X-ray images which SXI will generate. This work, simulating the changes which can be expected in magnetospheric boundary locations under differing solar wind conditions, coupled with investigations of how to extract magnetospheric boundary and cusp positions, is essential in order to optimise the SXI observing strategy once SMILE is operational. The WG is very active, with monthly teleconferences where research work is reported and discussed in detail. The WG has also been meeting face-to-face on the occasions of SWT and Consortium meetings, with one day of presentations and workshop-type discussions proceeding the SWT and Consortium gatherings. The WG website can be found here.
SMILE Science Study Team, now renamed SMILE Science Working Team
The SMILE Science Study Team (SST) met every few months since the mission was chosen for the initial study phase, normally at ESA ESTeC with teleconference participation from China. Since the end of 2017 the SST has been meeting in conjunction with the SMILE Consortium meetings. Following SMILE Adoption in 2019 the SST has been renamed the SMILE Science Working Team or SWT. The SWT executive team includes the mission Co-PIs, payload PIs, the ESA Project Scientist and Project Manager, as well as the CAS Project Manager. Participation to the SWT meetings joint with Consortium meetings is open to instrument Co-Is and developers, ESA and CAS scientists, engineers and managers, and the scientific community with an interest in SMILE. One of the main tasks of the SWT is to develop and maintain the SMILE Science Requirement Document, which describes the mission science objectives and science requirements, and to ensure that the derived performance requirements for the payload will deliver the science expected from SMILE.
SMILE Science Advisory Panel (SAP)
The establishment of the SMILE Science Advisory Panel (SAP) has been promoted by the UK Space Agency (UKSA) in order to enable the provision of expert advice on issues relevant to the development of the SMILE mission and in particular of the Soft X-ray Imager, which constitutes the main UK hardware responsibility in the mission. The SAP also acts as a forum for monitoring the SXI development in order to achieve its science requirements, and advises the project when issues relating to the instrument performance arise, as well as on planned operations and data products.
In addition, the SAP is expected to provide expert advice on how to exploit the full complement of the SMILE payload in order to enable ground-breaking science to be carried out; to advise on key science open questions that could be tackled with SXI data and SMILE as a whole, and raise topical issues that may not have received adequate attention; to suggest public engagement opportunities generated by SMILE and the SXI in particular, and help to scope and develop a SMILE Benefits Management framework. The SAP is expected to provide reports and recommendations to the SMILE mission Co-PI, the SXI PI and the UKSA Project Management Board.
Source: SMILE-Spacecraft, Smile-Meeting
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