An idea of Space mm/sub- mm VLBI Array Xiao-Yu Hong ( 洪晓瑜 ) Jun-Hui Zhao ( 赵军辉 ) Zhi-qiang Shen ( 沈志强 ) Shanghai Astronomical Observatory ( 中国科学院上海天文台 )

1.VLBI in China 2.VLBI in the world 3.Scientific requirement for Higher resolution 4.VLBI in future 5.How to find the DIRECT evidence of BH? 6.An idea of Space mm/sub-mm VLBI Array Outline

1. VLBI in China Seshan radio telescope Shanghai Correlator Nanshan radio telescope

Regular VLBI observations of Sheshan and Nanshan telescopes EVN (European VLBI network) IVS (International VLBI service for Geodesy and astrometry) APSG (Asia - pacific space geodynamics project ) VSOP (Shanghai telescope joint VSOP survey program) Some other ad hc VLBI observation

VLBA VSOP Australian LBA & APT VERA 2.VLBI Facilities around the world The Global mm-VLBI Array

3. Scientific requirement for Higher resolution Radio jet & Black hole physics Radio source evolution Astrometry Galactic and extra-galactic Masers Gravitational Lenses SNR and GRB studies Nearby and distant starburst galaxies Nature of faint radio source population HI absorption studies in AGN…

4.VLBI in future VLBI contributes the highest resolution in modern Astronomy The very high angular resolution of VLBI can be increased further in two ways: either by using longer baselines (to space) or by observing at shorter wavelengths (mm and sub-mm wavelength). B

4.1 The Global mm-VLBI Array

mm-VLBI is now able to provide good quality images in the 3mm band, with an angular resolution of typically micro-arcseconds. At shorter wavelengths the VLBI technique is still in its development stage [although first detections were recently made at 2mm (129, 147 GHz) and at 1.3mm (215 and 230 GHz)]. an angular resolution which is unsurpassed by any other present astronomical imaging method.

4.2 SMA SMA: 8 X 6 米 ; Baseline: 8mto 508m; SMA located at Mauna kea; Frequencies:180GHz to 900GHz.

4.3 ALMA 64 X 12 m Longest baseline:14 kilometers Frequencies: 70 to 900 GHz. ALMA will be the most powerful sub-mm array on the ground in next 30 years

4.4 Space VLBI VSOP ARISE RadioAstron VSOP2 Space VLBI Array?

Angular resolution: Ground-based VLBI: VSOP: VLBI beyond the Earth diameter: VSOP mission ISAS, Japan + world-wide collaboration (in orbit since 1997)

Advance Radio Interferometry between Space and Earth

RadioAstron

VSOP-2 (Japan)

5. How to find the DIRECT evidence of BH? Candidate Objects? Which observed frequencies? In radio bands: facilities?

What is the most possible of 10 candidates? NGC 4258? MGC 4261? M87? 3C273? 3C345? 3C279? ? ? First 20? First 50? 5.1 Candidate Objects?

5.2 Which frequencies: Gamma ray? X-ray? UV? Optical? Infrared? Radio? Sub-mm? mm? cm?

5.3 Radio: facilities Single Disk? SMA? ALMA? VLBI: VLBA? EVN? The Global mm VLBI Array? VSOP? VSOP-2 Space mm/sub-mm VLBI array?

5.4 Space mm/sub-mm VLBI Array (SMVA)? Sensitivity request? Distance of baseline request? Frequencies request? > 100 GHz to TGHz? (u,v) coverages?

6. An idea of Space mm/sub- mm VLBI Array Antennas: 5 or 6 antennas with diameters in 2 meters No puckering is need -> good for high frequencies One rocket with all the satellites Sensitivity request? Lower cost to current VSOP ideas

Orbit design: Obtaining good (u,v) coverages Distance of baseline request Orbit measure: GPS, Laser, Ground VLBI Maser?

谢谢！ Thank you!