Introduction: In China's third lunar exploration project Chang'E-3 mission, a lander and a rover will be placed on the lunar surface. The lander will not be movable, and the rover will explore the Moon automatically. The rover will be in moving and standstill state interchangeably [1].The precise positioning of the lander and the rover is very important in Chang'E-3 mission. This paper focuses ...

Due to its proximity, M87 is a prime target for next-generation high-resolution VLBI at short millimeter wavelengths, by which the jet launching region and the black hole shadow are expected to be resolved and imaged sometime soon. Along with this situation, high-quality VLBI imaging and monitoring at lower frequencies play an important role in complementing the high-frequency data. Here, we pr...

Obtaining a census of active galactic nuclei (AGN) activity across cosmic time is critical to our understanding galaxy evolution and formation. Many AGN classification techniques are compromised by dust obscuration. However, very long baseline interferometry (VLBI) can be used identify compact emission that only attributed activity. This the second in series papers dealing with radio population...

Multiple-epoch phase-referenced VLBI observations of 11 radio-emitting stars have been conducted as part of an astrometric program to link the Hipparcos optical reference frame to the radio extragalactic reference frame. We present the VLBI positions, proper motions and trigonometric parallaxes from this program in the ICRF (International Celestial Reference Frame). These astrometric parameters...

A Kalman filter was developed to combine VLBI estimates of UT1-TAI with biased length of day (LOD) estimates from GPS. The VLBI results are the analyses of the NASA Goddard Space Flight Center group from 24-hr multi-station observing sessions several times per week and the nearly daily 1-hr single-baseline sessions. Daily GPS LOD estimates from the International GNSS Service (IGS) are combined ...

We observed SDSS J0836+0054, the most distant radio-loud quasar known at present (z = 5.774) with the European Very Long Baseline Interferometry (VLBI) Network at the 5 GHz frequency on 2003 November 4. The source is compact at the milli-arcsecond (mas) angular scale with a flux density of 0.34 mJy. The observations with the Very Large Array (VLA) made on the consecutive day support a conclusio...

A demonstration at iGRID 2005 used dynamic, deterministic, and dedicated LightPath network services to link radio telescopes from around the world with computational facilities at the MIT Haystack Observatory to create a single coherent instrument for real-time astronomical and geodetic research. The “electronic Very Long Baseline Interferometry” (e-VLBI) application provides ultra-high resolut...

A 20-hour VLBI observation with the NRAO VLBA and GBT in the NOAO Boötes field reaches an rms noise of 9 microJy per beam at 1.4 GHz. Three sources were detected at 10-milliarcsecond resolution within the GBT primary beam of FWHM 8.6, including the 20milliJy calibrator and two sub-milliJy sources. By tapering the visibility data, portions of the VLBA primary beam of FWHM 29 were imaged at poore...

We discuss a technique for mapping the synchrotron turnover frequency distribution using nearly simultaneous, multi–frequency VLBI observations. The limitations of the technique arising from limited spatial sampling and frequency coverage are investigated. The errors caused by uneven spatial sampling of typical multi– frequency VLBA datasets are estimated through numerical simulations, and are ...

We present here two epochs of Space VLBI Observations at 18 cm of the BL-Lac type object Mkn 501. Thanks to the high resolution of these new data we have found that the inner jet is centrally brightened at its beginning but becomes extended and limb brightened at ∼ 8 mas from the core. Moreover a comparison between the two epochs shows the presence of a possible proper motion with apparent velo...