Solar Polar Orbit Radio Telescope (SPORT): A Mission Concept for Interplanetary CMEs ImagingWU Ji, LIU Hao, SUN Weiying, ZHENG Jianhua, FENG Xueshang, ZHANG Cheng, YANG Xuan, etc

National Space Science Center, Chinese Academy of Sciences (NSSC, CAS)

ContentsBackground & MotivationObjective: CME observationHow? Synthetic aperture imagingMission OverviewFrequency selectionSystem designOrbit designOther payloadsCurrent status & development planSummary

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

Mark IV coronagraphMLSO, Hawaii, Sep.7, 2005Nancay RadioheliographCME observations: Ground-based observation

CME observations: Spaceborne observation

1.BackgroundDue to the latitude effect and the rotation of the Sun, most of the CMEs are propagate near the ecliptic plane.

1. BackgroundTo observe the CMEs from solar polar orbit is expected in order to have an overall view of it and predict the direction of its propagation.

1. BackgroundIn order to observe the ICMEs (plasma clouds), radio frequency band is then proposed with the brightness temperature as the main physical parameter to measureHowever, 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 TechnologyOriginal SceneIts spatial Frequency Domain Representation

Synthetic Aperture Radio Telescope1980, VLA (Very Large Array)

ALMAAdvantage: 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 Observationfrom 1980s, L-band, for soil moisture & ocean salinity obsvationfrom 2000~, millimeter wave, 50~56GHz, for geostationary atmospheric sounding

Difference between Radio Astronomy & Earth ObservationSPORT is more like an earth observation system, which is intended for extended targets observation from space.

SPORT OverviewSystem Specifications Frequency: 150MHzBandwidth: 20MHzPolarization: CircularAngular Resolution 2Radiometric Sensitivity ~1K Imaging Period 30~60 minsFOV 25 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 selectionThermal free-free emission:

2.1 Frequency selectionBackground solar windWith 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 elementsClock Scan can realize uniform sampling of the spatial frequency domain2.2 System design

SPORT Artistic ViewStowedDeployedDimension of the seconds boom group: 35.76mDimension 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

1

ADC

I

Q

0 ~ 10 MHz

0 ~ 10 MHz

Digital Correlator

14010MHz

Power Divider

Central Unit

Antenna

LNA

Front-end

LOf=140MHz

Element Antenna/Receiver

IQ Mixer

PMS(Power Measurement System)

2.2 System design

2.2 System design

Antenna: Umbrella Deployment2.2 System design

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

2AU2.3 Orbit design

2.3 Orbit design

Optical instruments: such as chronographer, X-EUV imagers, Heliospheric Imager, etcIn situ measurement package: solar wind plasma detectors, both ion and electrons, energetic particle detector, fluxgate magnetometer, low frequency wave detector, solar radio burst spectrometer2.4 Other payloads

The concept of SPORT was proposed in 2004.Enhanced key technology and engineering feasibility studies 2008-2011with the support from CNSA.Frequency issues, sensitivity v.s. backgroundMain telescope (element channels)design and ground testImage retrieval algorithmsOrbit injection studiesICMEs propagation numerical simulation and theories2.4 Current study and development Schedule

Background engineering study (ongoing): 2011~2015, with the support from Strategic Priority Research Program - Space Science of the CASEngineering development may start 2016Launch date: March 2020In orbit observation start 2023-20242.4 Current study and development Schedule

SummarySPORT 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 instrumentsInternational participation is welcome

Thank You

*Once CMEs propagate toward Earth, geospace may be severely disturbed. As CMEs propagate in other directions, they may interact with other planets (e.g., Mars), and may also cause problems for interplanetary spacecraft during deep space exploration. *OSO-7:7The zodiacal light photometers :a Lyot white light coronagraph : LASCOThe Solar Mass Ejection Imager (SMEI) :white light (SECCHI) on board STEREO consists of five telescopes: an extreme ultraviolet imager, two traditional Lyot coronagraphs and two new designs of heliospheric imagers. With the launch of the SMEI and the STEREO mission in 2003 and 2006, respectively, CMEs can now be observed remotely all the way to the Earth [Lugaz et al., 2010]

*The SPORT mission will provide a completely new perspective of CMEs by remote sensing in radio wave band from solar polar orbit. It will track CMEs from a distance of a few solar radii to near 0.35 AU from solar polar orbit. The question of whether Earth, Mars or any deep space missions might be affected by CMEs could be answered more clearly. *The SPORT mission will provide a completely new perspective of CMEs by remote sensing in radio wave band from solar polar orbit. It will track CMEs from a distance of a few solar radii to near 0.35 AU from solar polar orbit. The question of whether Earth, Mars or any deep space missions might be affected by CMEs could be answered more clearly. *Plasma emission occurs at the plasma frequency and its second harmonic, but rarely if ever at higher harmonicsLCME*The measured value of the galactic-background emission from 15 to 300 MHz is about from 10^4 to 50 K .*The measured value of the galactic-background emission from 15 to 300 MHz is about from 10^4 to 50 K .