Related papers: Space VLBI at Low Frequencies
Global Positioning System (GPS) satellites broadcast at frequencies of 1,575.42 MHz (L1) and of 1,227.60 MHz (L2). The dispersive property of the ionosphere can be used to combine independent measurements at the two frequencies to estimate…
A second generation near-term space VLBI mission, VSOP-2, is being planned for a launch in 2010 or soon after. The scientific objectives are very high angular resolution imaging of astrophysically exotic regions, including the cores, jets,…
The low-frequency sky below $\sim$15 MHz (20 m) is obscured by the Earth's ionosphere, the layer of charged particles above the neutral atmosphere. Single spacecraft have made measurements in this band, but cannot achieve high or even…
We present a community study exploring the low frequency (5 - 800 MHz) options and opportunities for the ngVLA project and its infrastructure. We describe a Next Generation LOw Band Observatory (ngLOBO) that will provide access to the low…
We study the fundamental limits of detection for astrophysical observations in the far infrared. Understanding these fundamental limits is critical to the planning and analysis of experiments in this region. We specifically characterize the…
Optical Very Long Baseline Interferometry (VLBI) offers the potential for unprecedented angular resolution in both astronomical imaging and precision measurements. Classical approaches, however, face significant limitations due to photon…
In this paper I outline a new strategy for the routine detection and imaging of faint (sub-mJy and microJy) radio sources with VLBI and SVLBI. The strategy relies on a combination of in-beam phase-referencing, wide-field VLBI imaging and…
Ground based low frequency radio interferometers have been developed in the last decade and are providing the scientific community with high quality observations. Conversely, current radioastronomy instruments in space have a poor angular…
Low-frequency polarisation observations of pulsars, facilitated by next-generation radio telescopes, provide powerful probes of astrophysical plasmas that span many orders of magnitude in magnetic field strength and scale: from pulsar…
We propose a new kind of interferometric array that yields images of high dynamic range and large field. The numerous individual apertures in this array form a pattern related to a Fresnel zone plate. This array can be used for…
High-Frequency (HF) radar is well suited to the surveillance of low-Earth-orbit space. For large targets, a small deployable HF radar is able to match the detection performance of much larger space surveillance radar systems operating at…
The free-free absorption of low frequency radio waves by thermal electrons in the warm ionized medium of our Galaxy becomes very significant at $\lesssim 10$ MHz (ultralong-wavelength), and the absorption strength depends on the radio…
The apparent position of the "core" in a parsec-scale radio jet (a compact, bright emitting region at the narrow end of the jet) depends on the observing frequency, owing to synchrotron self-absorption and external absorption. While…
Interferometry in the optical and near infrared has so far played a marginal role in Extragalactic Astronomy. Active Galactic Nuclei are the brightest and most compact extragalactic sources, nonetheless only a very limited number could be…
Space-VLBI observations of stellar sources represent a challenge since there are few sources with sufficiently high brightness temperature for detection on space-ground baselines. X-ray binaries (XRB) are among the few types of stellar…
Remarkable progress has been made in understanding turbulent astrophysical plasmas in past decades including, notably, the solar wind and the interstellar medium. In the case of the solar wind, much of this progress has relied on in situ…
Compact galactic and extragalactic radio sources can be imaged with an unsurpassed angular resolution of a few ten micro-arcseconds, adopting the observing technique of global millimeter VLBI. Here we present the Global Millimeter VLBI…
Sky models have been used in the past to calibrate individual low radio frequency telescopes. Here we generalize this approach from a single antenna to a two element interferometer and formulate the problem in a manner to allow us to…
Kilometric-scale optical imagers seem feasible to realize by intensity interferometry, using telescopes primarily erected for measuring Cherenkov light induced by gamma rays. Planned arrays envision 50--100 telescopes, distributed over some…
Radio astronomical observations have very poor signal to noise ratios, unlike in other disciplines. On the other hand, it is possible to observe the object of interest for long time intervals as well as using a wider bandwidth.…