Detection of Line-shaped
Tracks in Images with
DADD
STScI
Peter R. McCullough
Jul 21, 2011
1
How fast we are progressing…



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
2/11
How fast we are progressing…



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)
3/11
DADD = Doubling Accumulation Drift Detection
DADD brought to you by …



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Cullers & Deans 1992, unpublished*, cited by
Backus, 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obtaining a scanned copy of this unpublished report.
4/11
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.
5/11
DADD = Doubling Accumulation Drift Detection
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.
M Times
M spectra, each with N channels
N Frequencies
6/11
DADD = Doubling Accumulation Drift Detection
00 00
00 11
01 12
01 23
0000 0000
0000 1111
0011 1122
0011 2233
0112 2334
0112 3445
0123 3456
0123 4567
continuous functions:
all steps = 0 or 1 channel
0001
0111
constant derivatives
M Times
00
01
N Frequencies
7/11
DADD is sensitive
8/11
DADD is sensitive, quick,
Execution time per track identified
= 0.7 seconds per megapixel
= 2.8 s for 2048x2048
9/11
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 preprocessing and post-processing analysis.
(WFC3 ISR coming soon)
10/11
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.
11/11