Speaker
Description
This talk presents a cost feasible remote sensing solution that we have developed to aid and improve the calibration of Murchison Widefield Array (MWA) measurements for ionospheric errors using small satellites. For polarimetry, a crucial step in the calibration of MWA measurements involves removing the polarization error due to ionospheric Faraday rotation (FR) with a sufficiently high precision to extract astronomical information. However, current calibration algorithms to correct for ionospheric FR are inherently limited by the accuracy and uncertainty of Global Navigation Satellite System based ionospheric total electron content (TEC) models and publicly available geomagnetic models on which they rely. As a direct consequence, polarization corrections currently have a rotation measure (RM) uncertainty of $\sim 0.1\,$rad/m$^2$. This yields an insufficiently precise calibration solution to enable the study of plasma due coronal mass ejections far from the sun and long-term variations of pulsars with the MWA, both of which are significant science goals in radio astronomy. A high-resolution source of southern mid-latitude ionospheric FR data with an uncertainty better than $0.015\,$rad/m$^2$ is needed to enable such polarimetric studies using the MWA.
To address this, we have been developing a new ionospheric measurement technique and 3U CubeSat beacon system. Our proposed solution is capable of delivering a direct source of southern mid-latitude ionospheric FR data with a RM uncertainty better than $0.015\,$rad/m$^2$. We achieve this by uniquely employing linearly polarized beacon signals, which enables us to directly measure ionospheric FR through plane of polarization measurements at a ground receiver station. Robust simulation results demonstrating our ionospheric measurement capabilities in the presence of system noise, weak scattering, clock errors and antenna characteristics will be presented. Early results from our developed beacon subsystems, including the small satellite antenna and RF transmitter, will also be shown. Further, I will also discuss that in solving this polarization calibration challenge, our solution has the potential to further aid and improve the calibration of MWA measurements for other ionospheric errors. That is, 1) improving phase calibration by providing high resolution ionospheric TEC data (with an uncertainty of $\leq 10\,$mTECU), and 2) improving scintillation noise calibration by providing native ionospheric scintillation noise measurements within the MWA band. Finally, I will also discuss the future work that is essential to successfully realize this ionospheric remote sensing solution.
| Timeslot preferences | 15/20 minutes |
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