Download - Detection of Line-shaped Tracks in Images with DADD STScI Peter R. McCullough Jul 21, 2011 1
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Detection of Line-shaped Tracks in
Images with DADD
STScI
Peter R. McCulloughJul 21, 2011
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2007, First Map of an Alien World, SST press release for Nature article of Knutson et al.
2009, Alien Maps of an Ocean-bearing World, ApJ title of Cowan et al.
2011, Observational Evidence of Sentient Life on an Earth-like Planet, TIPS alternative title of McCullough
How fast we are progressing…
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2007, First Map of an Alien World, SST press release for Nature article of Knutson et al.
2009, Alien Maps of an Ocean-bearing World, ApJ title of Cowan et al.
2011, Observational Evidence of Sentient Life on an Earth-like Planet, McCullough (this work)
How fast we are progressing…
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Jill Tarter, JHU seminar 2004-2005 Richard Stauduhar (1940-2010), mathematician
for the SETI Institute and U.C. Berkeley Space Sciences Lab, private communication 2005.
Cullers & Deans 1992, unpublished*, cited byBackus, P. R. 1993, The NASA SETI Microwave Observing project Targeted Search, in Third Decennial US-USSR Conference on SETI, ASP Conference Series, Vo. 47, p. 323.
SetiQuest.org, sonata-1.0.16.zip
* thanks to Jill Lagerstrom (and the authors) for obtaining a scanned copy of this unpublished report.
DADD brought to you by …
DADD = Doubling Accumulation Drift Detection
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Line-shaped streaks (from bright lights on Earth) appear in ~30% of HST WFC3 observations of the dark-side of Earth, (taken for flat fields, to be described in a future TIPS). DADD automates flagging of pixels within streaks.
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DADD = Doubling Accumulation Drift Detection
M spectra, each with N channels
Requirement of slow drift: |slope| > 1
Mathematical operations:Brute force: ~2NM2
DADD: ~2 NM log2 M
DADD accumulates pairwise like the FFT ;DADD reuses sums of pixels common to multiple lines across the 2-D array.
To apply DADD to 2-D imagery, we analyze the image successively four times with rotations of 0º, 90º, 180º, and 270º in order to detect trails of arbitrary slope and origin.
N FrequenciesM
Tim
es
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DADD = Doubling Accumulation Drift Detection
0 0 continuous functions:0 1 all steps = 0 or 1 channel
00 00 0001 constant derivatives00 11 011101 1201 23
0000 00000000 11110011 11220011 22330112 23340112 34450123 34560123 4567
N FrequenciesM
Tim
es
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DADD is sensitive
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DADD is sensitive, quick,
Execution time per track identified
= 0.7 seconds per megapixel= 2.8 s for 2048x2048
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DADD is sensitive, quick, and stands alone
Execution time per track identified
= 0.7 seconds per megapixel= 2.8 s for 2048x2048
C code operating on 16-bit FITS 2-D images, with an IDL wrapper to facilitate pre-processing and post-processing analysis.
(WFC3 ISR coming soon)
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Summary: DADD can be used for detection of …
1. SETI signals, e.g. weak, drifting narrowband CW signal in time series of RF spectra
2. Streaks across dark-Earth flat-fields (as illustrated)3. Cosmic ray trails*4. Asteroid or satellite trails*5. Bleeding (overexposed PSF) trails* ^ 6. Slitless grism spectra* ^
* DADD is less sensitive to shorter line segments.^ DADD is probably overkill where orientation of trails is fixed and known a priori.
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