Dynamic tunable notch filters for the Antarctic Impulsive Transient Antenna (ANITA)

TL;DR

This paper describes the deployment and successful operation of tunable notch filters on ANITA-IV, which reduced noise and increased instrument livetime in the search for ultra-high-energy neutrinos.

Contribution

Introduction and implementation of tunable notch filters (TUFF boards) in ANITA-IV to mitigate narrow-band noise and improve data collection efficiency.

Findings

TUFF boards operated successfully during ANITA-IV flight.

Noise mitigation led to a 2.8 times increase in instrument livetime.

Enhanced signal processing improved neutrino detection prospects.

Abstract

The Antarctic Impulsive Transient Antenna (ANITA) is a NASA long-duration balloon experiment with the primary goal of detecting ultra-high-energy ($>10^{18}\,\mbox{eV}$) neutrinos via the Askaryan Effect. The fourth ANITA mission, ANITA-IV, recently flew from Dec 2 to Dec 29, 2016. For the first time, the Tunable Universal Filter Frontend (TUFF) boards were deployed for mitigation of narrow-band, anthropogenic noise with tunable, switchable notch filters. The TUFF boards also performed second-stage amplification by approximately 45 dB to boost the $\sim\,\mu\mbox{V-level}$ radio frequency (RF) signals to $\sim$ mV-level for digitization, and supplied power via bias tees to the first-stage, antenna-mounted amplifiers. The other major change in signal processing in ANITA-IV is the resurrection of the $90^{\circ}$ hybrids deployed previously in ANITA-I, in the trigger system, although in this paper we focus on the TUFF boards. During the ANITA-IV mission, the TUFF boards were successfully operated throughout the flight. They contributed to a factor of 2.8 higher total instrument livetime on average in ANITA-IV compared to ANITA-III due to reduction of narrow-band, anthropogenic noise before a trigger decision is made.