skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Coherent Time-domain Canceling of Interference for Radio Astronomy
Abstract Radio astronomy is vulnerable to interference from a variety of anthropogenic sources. Among the many strategies for mitigation of this interference is coherent time-domain canceling (CTC), which ideally allows one to “look through” interference, as opposed to avoiding the interference or deleting the afflicted data. However, CTC is difficult to implement, not well understood, and at present this strategy is not in regular use at any major radio telescope. This paper presents a review of CTC including a new comprehensive study of the capabilities and limitations of CTC using metrics relevant to radio astronomy, including fraction of interference power removed and increase in noise. This work is motivated by the emergence of a new generation of communications systems which pose a significantly increased threat to radio astronomy and which may overwhelm mitigation methods now in place.  more » « less
Award ID(s):
2029948
PAR ID:
10445699
Author(s) / Creator(s):
;
Date Published:
Journal Name:
Publications of the Astronomical Society of the Pacific
Volume:
134
Issue:
1041
ISSN:
0004-6280
Page Range / eLocation ID:
114505
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; (, IEEE)
    This paper describes methods for accurate pattern modeling of large axisymmetric paraboloidal focus-fed reflector antenna systems. We demonstrate that the incorporation of the developed pattern models helps in advancing the state-of-the-art in coherent time-domain canceling (CTC) for interference mitigation in radio astronomy. The first method yields a closed form expression for the antenna pattern with parameters accounting for the focal ratio and feed pattern. In subsequent adaptive methods, parameters of this model are calculated using measurements of interference signals. The corrected pattern model improves the prediction of the change in the true pattern for future times. The methods are compared by (1) comparing the error in the pattern model with respect to the true pattern and (2) comparing the pattern value update period required to achieve a specified level of residual interference when used in CTC. The efficacy of the pattern modeling methods is demonstrated by showing that the error in the pattern model decreases and the pattern value needs to be updated at a much slower rate for effective CTC. 
    more » « less
  2. ; ; (, Publications of the Astronomical Society of the Pacific)
    Abstract Anthropogenic interference has been a long-standing problem for radio astronomy. In a previous paper, we presented a study of interference mitigation methods based on the concept of coherent time-domain canceling, which ideally allows one to “look through” interference, as opposed to avoiding the interference or deleting the afflicted data. The focus of that paper was on “reference antenna” methods, in which a separately acquired signal containing the interference waveform is used to identify the interference waveform in the primary signal. In this paper, we shift focus to methods in which the reference signal is instead a parametric model of the waveform, so that no additional antenna is needed. As in our previous paper, we present a rigorous theoretical analysis of performance. Findings are demonstrated using real-world interference from the Iridium system. We find that interference suppression is possible if the product of the interference-to-noise ratio and the number of statistically independent samples is greater than 1, and that suppression increases linearly with this product. However good performance is achieved only for interferers whose bandwidth is much less than the sample rate, and algorithm parameters must be carefully selected to avoid undesirable distortion of the noise spectral baseline. 
    more » « less
  3. ; ; ; (, Journal of Astronomical Instrumentation)
    Direction of arrival (DoA) estimation plays a crucial role in various areas of signal processing. Although existing methods perform satisfactorily at moderately high signal-to-noise ratio (SNR) levels of the order of 0 dB, they often lack accuracy in low SNR scenarios ([Formula: see text]10 dB), which is critical in science applications like radio frequency interference (RFI) mitigation for radio astronomy. In this context, it is essential to estimate the DoA of a source of RFI at low SNR to prevent high-gain radio telescope receivers from saturating. In this paper, a novel DoA estimation method is proposed, which is designed specifically for low SNR scenarios. This method involves multiple subarrays and decomposition techniques to enhance the SNR of the RFI. By comparing the signal subspace with the noise subspace, we can identify the potential incident direction and perform refinement in subsequent steps. Accuracy is further improved by combining all DoA candidates together and utilizing a clustering method to remove outliers. We conducted simulations using Automatic Dependent Surveillance-Broadcast (ADS-B) signals and sine waves in Additive White Gaussian Noise (AWGN) and multipath fading channels for signals that will be detected by a 100[Formula: see text]m radio telescope. The results demonstrate that our proposed method outperforms prior algorithms in low SNR conditions. 
    more » « less
  4. ; ; ; ; (, European Space Agency Space Debris Office)
    Lemmens, S; Flohrer, T; Schmitz, F (Ed.)
    Radio telescopes observe extremely faint emission from astronomical objects, ranging from compact sources to large scale structures that can be seen across the whole sky. Satellites actively transmit at radio frequencies (particularly at 10±20 GHz, but usage of increasing broader frequency ranges are already planned for the future by satellite operators), and can appear as bright as the Sun in radio astronomy observations. Remote locations have historically enabled telescopes to avoid most interference, however this is no longer the case with dramatically increasing numbers of satellites that transmit everywhere on Earth. Even more remote locations such as the far side of the Moon may provide new radio astronomy observation opportunities, but only if they are protected from satellite transmissions. Improving our understanding of satellite transmissions on radio telescopes across the whole spectrum and beyond is urgently needed to overcome this new observational challenge, as part of ensuring the future access to dark and quiet skies. In this contribution we summarise the current status of observations of active satellites at radio frequencies, the implications for future astronomical observations, and the longer-term consequences of an increasing number of active satellites. This will include frequencies where satellites actively transmit, where they unintentionally also transmit, and considerations about thermal emission and other unintended emissions. This work is ongoing through the IAU CPS. 
    more » « less
  5. ; (, IEEE)
    Signals from satellites are a source of interference to radio telescopes. One possible scheme for mitigation of this interference is coherent time-domain canceling. Using a simple but broadly-applicable model for the antenna pattern, we show how the antenna pattern combined with the motion of the satellite limits the time available to compute an accurate estimate of the interference waveform, which subsequently limits the extent to which interference can be canceled in the output. We suggest a simple remedy to the problem. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email