Solar Polar Orbit Radio Telescope (SPORT): A Mission Concept for Interplanetary CMEs Imaging WU Ji, LIU Hao, SUN Weiying, ZHENG Jianhua, FENG Xueshang, ZHANG Cheng, YANG Xuan, etc National Space Science Center, Chinese Academy of Sciences (NSSC, CAS)

Contents Background & Motivation −Objective: CME observation −How? Synthetic aperture imaging Mission Overview −Frequency selection −System design −Orbit design −Other payloads −Current status & development plan Summary

1. Background Coronal Mass Ejections (CMEs) are expulsions of coronal plasmas and magnetic fields from the Sun. CME The detection of CMEs between the Sun and the Earth is important for understanding and ultimately predicting space weather conditions.

Mark IV coronagraph MLSO, Hawaii, Sep.7, 2005 Nancay Radioheliograph CME observations: Ground-based observation

CME observations: Spaceborne observation

1.Background Due to the latitude effect and the rotation of the Sun, most of the CME’s are propagate near the ecliptic plane.

1. Background To observe the CME’s from solar polar orbit is expected in order to have an overall view of it and predict the direction of its propagation. SPORT SunEarth

1. Background In order to observe the ICMEs (plasma clouds), radio frequency band is then proposed with the brightness temperature as the main physical parameter to measure However, to image at radio frequency need a very large antenna aperture and also to scan it. We need to select an accepted physical aperture of the antenna by a minimum spatial resolution

How can we get required spatial resolution from Solar Polar Orbit at radio frequency? Synthetic Aperture Imaging Technology Original Scene Its spatial Frequency Domain Representation

Synthetic Aperture Radio Telescope 1980, VLA (Very Large Array)ALMA Advantage: to get very high angular resolution that can not be achieved by traditional real aperture reflector antenna system due to physical aperture size restriction!

Microwave Synthetic Aperture Radiometer: for Earth Observation from 1980’s, L-band, for soil moisture & ocean salinity obsvation from 2000~, millimeter wave, 50~56GHz, for geostationary atmospheric sounding

Difference between Radio Astronomy & Earth Observation SPORT is more like an earth observation system, which is intended for extended targets observation from space. Radio AstronomyEarth Observation Target Field Of ViewSmall Scale TargetDistributed Target (several tens degree) Spatial ResolutionArc-secondsDegrees, minutes Sampling requirement in spatial frequency domain Sparse samplingFull sampling

SPORT Overview System Specifications –Frequency: 150MHz –Bandwidth: 20MHz –Polarization: Circular –Angular Resolution ： 2º –Radiometric Sensitivity ： ~1K –Imaging Period ： 30~60 mins –FOV ： ±25º SPORT SunEarth Observing Geometry

2.1 Frequency selection Interplanetary CMEs may exhibit three relevant radio emission mechanisms: bremsstrahlung, gyrosynchrotron emission and plasma emission. Bremsstrahlung is produced by Coulomb collisions between charged particles in plasmas. Gyrosynchrotron emission is the electromagnetic emission generated by mildly relativistic electrons moving in a magnetic field. Plasma emission is generated by plasma instabilities, wave- wave and/or wave-particle interactions.

2.1 Frequency selection Thermal free-free emission:

2.1 Frequency selection Background solar wind With Interplanetary CMEs

2.1 Frequency selection Background brightness temperature

2.1 Frequency selection Background brightness temperature

Using the clock scan scheme, the main telescope will have two groups of element antennas and their receiving channels, each composed of four elements Clock Scan can realize uniform sampling of the spatial frequency domain 2.2 System design

SPORT Artistic View StowedDeployed Dimension of the “seconds boom” group: 35.76m Dimension of the “minutes boom” group: 31.76m

2.2 System design Antennas: to receive the of radio emissions of the CME & galactic background Receivers: to amplify the received noise IQ down-conversion Digital Correlators: to get the visibilities PMS: total power measurement LO & Power Divider: to provide a common LO

2.2 System design

Antenna: “Umbrella” Deployment 2.2 System design

Case 1: Case 2: 2.2 System design – imaging simulation

The orbit of SPORT is designed to follow the Ulysses orbit with a swing by Jupiter to get enough energy to escape from the ecliptic plane: 2.3 Orbit design

2AU 2.3 Orbit design

Optical instruments: –such as chronographer, X-EUV imagers, Heliospheric Imager, etc In situ measurement package: –solar wind plasma detectors, both ion and electrons, energetic particle detector, fluxgate magnetometer, low frequency wave detector, solar radio burst spectrometer 2.4 Other payloads

 The concept of SPORT was proposed in  Enhanced key technology and engineering feasibility studies ， with the support from CNSA.  Frequency issues, sensitivity v.s. background  Main telescope (element channels)design and ground test  Image retrieval algorithms  Orbit injection studies  ICMEs propagation numerical simulation and theories 2.4 Current study and development Schedule

Background engineering study (ongoing): 2011~2015, with the support from “Strategic Priority Research Program - Space Science” of the CAS Engineering development may start 2016 Launch date: March 2020 In orbit observation start Current study and development Schedule

Summary  SPORT will be probabaly the first mission taking image of the interplanetary CME from the solar polar orbit (>38 degrees)  It will provide unique overall view of the interplanetary CME not only on the Sun – Earth line but all around using radio frequency band and optical instruments  International participation is welcome

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