Interference Mitigation Tests at Molonglo

Daniel Mitchell, Duncan Campbell-Wilson, Frank Briggs

Overview

● RFI mitigation is likely to play an important role in SKAMP data processing.

● The wide bandwidth alone will open the telescope up to a much greater level of RFI.

● Have done some short, preliminary observations with and without RFI to see how effective mitigation is likely to be.

Preliminary RFI Tests.

● MOST has 88 bays (antennas), which will be cross-correlated with all of the others

➔ 88 input correlator.

● Correlator will have 96 inputs➔ Room for RFI reference antennas.

➔ Use closure relation based "post-correlation" cancellation algorithm to test RFI reduction.

● RFI - Broad-band noise from the RFI site:➔ Estimated 5000 computer equivalents

➔ Telemetry link to transmitter, variable attenuator & white noise source

● 4 IFs & Sampler box:➔ Two 778m x 12m MOST arms (with bay masking)

➔ Two orthogonal polarisations from the 6m dish

➔ Record to a PC at 16 Msamples / second / IF

RFI Test Range

Short Baselines (bays E01 & W01)

Short Baselines (bays E01 & W01)

Short Baselines (bays E01 & W01)

Short Baselines (bays E01 & W01)

Short Baselines (bays E01 & W01)

Short Baselines (bays E01 & W01)

Medium Baselines (bays E22 & W22)

Medium Baselines (bays E22 & W22)

Medium Baselines (bays E22 & W22)

Long Baselines (bays E44 & W44)

Long Baselines (bays E01 & W01)

Long Baselines (bays E01 & W01)

Summary

● RFI mitigation is likely to play an important role in SKAMP data processing.

● The wide bandwidth alone will open the telescope up to a much greater level of RFI.

● A preliminary look at cancelling RFI from single bay cross-correlations seemed to work well on three baseline scales.