Time Smearing in Space-based 3D Synthesis Imaging

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Abstract

Space-based radio astronomy is a great step for future research towards frequencies below 30 MHz. Science at these frequencies is interesting as it is expected that, amongst other science cases, we can uncover more information about the earliest times of our universe, the Dark Ages. These observations cannot be done on Earth as our ionosphere heavily distorts below 30 MHz and completely blocks signals below 10 MHz. The solution for this, is to move radio telescopes into space in the form of a large constellation of satellites that act as one giant virtual radio telescope using interferometry. Due to the size of the constellation, the needed downlink capacity to transfer all the data to Earth, is very demanding. One way to limit the downlink requirement is by using averaging in bandwidth or time. In a 2D, or planar, array, this results in smearing due to the movement of the satellites relative to the sources. Previously it was shown that frequency smearing can be minimized due to the well filled 3D constellation of satellites as the smearing is projected in the radial part. However, this research shows via simulations that although it is beneficial to increase the integration time, the use of a 3D constellation of satellites does come with new challenges. Due to decorrelation, the feasible integration time is limited to only a few tens to hundreds of milliseconds in a lunar orbit, which is caused by the changing distances and relative positions of each satellite to each other. Simulations are performed using the Orbiting Low Frequency Array (OLFAR) as reference for this study. The decorrelation can be limited by making use of Dynamic Baseline Dependent Averaging. When looking at the dynamics of a constellation in space, the rate of the change of the baseline lengths can be used as a reference to determine the integration time. In this paper this is referred to as Dynamic Baseline Dependent Averaging. Using the latter technique, in combination with a simple scheme a data reduction of more than 90% can be achieved.

Original languageEnglish
Title of host publication2022 IEEE Aerospace Conference, AERO 2022
PublisherInstitute of Electrical and Electronics Engineers
Number of pages8
ISBN (Electronic)978-1-6654-3760-8
DOIs
Publication statusPublished - 10 Aug 2022
Event2022 IEEE Aerospace Conference, AERO 2022 - Big Sky, United States
Duration: 5 Mar 202212 Mar 2022

Conference

Conference2022 IEEE Aerospace Conference, AERO 2022
Country/TerritoryUnited States
CityBig Sky
Period5/03/2212/03/22

Bibliographical note

Funding Information:
The author would like to thank the Center for Astronomical Instrumentation (CAI) for their support and funding which made this research possible.

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