We apply an efficient selection method to identify potential weak Very Long Baseline Interferometry (VLBI) target quasars simply using optical (SDSS) and low-resolution radio (FIRST) catalogue data. Our search is restricted to within 12 from known compact radio sources that are detectable as phase-reference calibrators for ASTRO-G at 8.4 GHz frequency. These calibrators have estimated correlate...

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 ...

برای دستیابی به مزیت رقابتی در شرایط عدم‌­اطمینان که آن تغییر ضروری است، یکی از چالش‌های بزرگ سازمان‌ها کاهش ریسک طریق ایجاد زنجیره‌های تأمین تاب‌آور است. تاب‌آوری زنجیره ‌تأمین توانایی مقابله با اختلال اشاره دارد یک رویداد غیرقابل‌پیش‌بینی بوده و دارای منابع داخلی خارجی مختلفی ازجمله بلایای طبیعی ریسک‌های عملیاتی پژوهش حاضر شبیه‌سازی توسط نرم‌افزار ارنا زنجیره‌ سنگ ساختمانی «کارخانه سنگبری آسم...

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...