Sky coverage as a function of FFT length

Each FFT length F has an associated duration D(F). If a spike of that FFT length is found during an observation shorter than D(F), it's probably RFI.

FFT bins begin at regularly-spaced times. An observation of duration 2*D(F) contains at least one FFT bin in its entirety, and an observation of duration 3*D(F) contains two.

Multiplets have at least two time-disjoint detections. Thus to find a multiplet composed of spikes of FFT length F in a pixel P, our observations of P must include two disjoint intervals of duration D(F). This is always the case if P has

an observation of duration at least 3*D(F), or
two observations of duration at least 2*D(F).

It is possibly the case if P has

an observation of duration at least 2*D(F), or
two observations of duration at least D(F).

We call these conditions 'strong' and 'weak' respectively. For each FFT length, here are the counts of pixels having the above properties.

FFT duration	# pixels, strong	% of pixels, strong	# pixels, weak	% of pixels, weak
8	15399958	100	15399958	100
16	15399958	100	15399958	100
32	15399958	100	15399958	100
64	15399958	100	15399958	100
128	15399958	100	15399958	100
256	15399958	100	15399958	100
512	15358403	99.730162	15362358	99.755843
1024	15003663	97.426649	15243071	98.98125
2048	14401001	93.513249	14922394	96.898927
4096	12057337	78.29461	14089389	91.489788
8192	7804281	50.677288	10933704	70.998272
16384	6554602	42.562467	7460499	48.444931
32768	3300343	21.430857	5849600	37.984519
65536	372334	2.41776	1788447	11.613324
131072	344996	2.24024	365336	2.372318

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