  A space-based very long baseline interferometry (VLBI) programme, named as
the Cosmic Microscope, is proposed to involve dual VLBI telescopes in the space
working together with giant ground-based telescopes (e.g., Square Kilometre
Array, FAST, Arecibo) to image the low radio frequency Universe with the
purpose of unraveling the compact structure of cosmic constituents including
supermassive black holes and binaries, pulsars, astronomical masers and the
underlying source, and exoplanets amongst others. The operational frequency
bands are 30, 74, 330 and 1670 MHz, supporting broad science areas. The mission
plans to launch two 30-m-diameter radio telescopes into 2,000 km x 90,000 km
elliptical orbits. The two telescopes can work in flexibly diverse modes: (i)
space-ground VLBI. The maximum space-ground baseline length is about 100,000
km; it provides a high-dynamic-range imaging capacity with unprecedented high
resolutions at low frequencies (0.4 mas at 1.67 GHz and 20 mas at 30 MHz)
enabling studies of exoplanets and supermassive black hole binaries (which emit
nanoHz gravitational waves); (ii) space-space single-baseline VLBI. This unique
baseline enables the detection of flaring hydroxyl masers, and more precise
position measurement of pulsars and radio transients at milli-arcsecond level;
(iii) single dish mode, where each telescope can be used to monitor transient
bursts and rapidly trigger follow-up VLBI observations. The large space
telescope will also contribute in measuring and constraining the total angular
power spectrum from the Epoch of Reionization. In short, the Cosmic Microscope
offers astronomers the opportunity to conduct novel, frontier science.
