| Abstract : | A number of ground- and space-based experiments are attempting to detect the faint redshifted
global 21-cm signal arising from the Cosmic Dawn (CD) and Epoch of Reionization (EoR).
Ground-based experiments face three unique challenges, namely i) ionospheric distortions ii)
coupling of the antenna properties to the Earth beneath and iii) terrestrial radio frequency
interference (RFI). Terrestrial RFI is particularly challenging as the FM radio band spanning over
87-108 MHz lies entirely within the frequency range of experiments targeting the 21-cm signal
from CD/EoR (~40-250 MHz). Several space-based experiments have been proposed to operate in
the radio-quiet region on the lunar farside. PRATUSH (Probing ReionizATion of the Universe using
Signal from Hydrogen) is a proposed lunar orbiter experiment from India with a primary science
goal of detecting the sky-averaged 21-cm signal from CD/EoR on the lunar farside. An intermediate
option in cost and complexity is deploying an experiment in space in an orbit around Earth. Our
algorithm - STARFIRE (Simulation of TerrestriAl Radio Frequency Interference in oRbits around
Earth) - provides an expectation of RFI in the FM band at different altitudes and spectral variation
around Earth. STARFIRE uses, as its input, a database of FM transmitters from around the world.
Applications of STARFIRE include identifying relatively RFI clean orbits around Earth, generating
RFI heatmaps and spectra. STARFIRE can be easily adapted for different frequencies, altitudes,
antenna properties, and terrestrial RFI databases. In this work, we explore low-interference orbits
around Earth for a PRATUSH like CD/EoR experiment. |
