Space Rocks! A Python Toolbox Tool for Asteroid Hazards' Body-Fixed Coordinate Extraction · 2019....

Space Rocks! A Python Toolbox Tool for Asteroid Hazards' Body-Fixed Coordinate Extraction

BY JON CUTTS – MS-GIST 2018

Image © University of Arizona

OSIRIS-REx: Asteroid Sample Return Mission Origins, Spectral Interpretation, Resource Identification, and Security–

Regolith Explorer” (OSIRIS-REx)

◦ “Prime objective of the OSIRIS-REx mission is to return pristine

carbonaceous regolith from [asteroid] Bennu”

(Lauretta, et al., 2017, page 5)

◦ University of Arizona led with NASA as stakeholder

◦ Dr. Dante Lauretta is the Principal Investigator of the OSIRIS-REx Mission, and a

University of Arizona professor

◦ Launched in September 2016 from Cape Canaveral, FL

Accomplishing the Mission High-resolution cameras will provide images of asteroid

◦ OSIRIS-REx Camera Suite (OCAMS) built by

University of Arizona

◦ 3 cameras with different field of views (FOVs)

◦ 1,000 pixel-wide images will be mosaiced

Spectrometers and a laser altimeter (LIDAR)

will provide additional information on

asteroid temperature, mineral composition,

and topography

OSIRIS-REx Camera Suite (OCAMS) Image © University of Arizona/Symeon Platts

OSIRIS-REx Instruments Cameras (OCAMS):

• POLYCAM, MAPCAM, SAMCAM

Spectrometers:

• OVIRS, OTES, REXIS

LIDAR:

• OLA

Sample Collection:

• TAGSAM

Image © NASA/Goddard/University of Arizona

Selecting a Sample-Site on the Asteroid Mission-critical decision of asteroid sample-site selection

◦ Mission requirement: collect at least 60 grams of regolith

◦ Regolith can be thought of as a carbonaceous asteroid’s “soil” layer

◦ Spacecraft instrument data used for four thematic maps:

1. Deliverability map: ability for the spacecraft to be “delivered” within 25m of sample-site

2. Safety map: safety to OSIRIS-REx’s sample-collecting instrument arm

3. Sampleability map: ability of the site to allow collection of 60g of regolith

4. Science Value map: ability of the site to offer a pristine, scientifically-valuable sample

Asteroid image © NASA/Goddard/University of Arizona

Rock and Boulder Identification Rocks and boulders are hazardous to the OSIRIS-REx spacecraft

◦ Identified by users using the images taken by the onboard cameras, OCAMS

◦ Locations stored as

features in shapefiles

◦ Locations of hazards will

be used as one of many

inputs to the Sampleability

and Science Value maps

◦ Polyline features allow for approximation of a boulder’s center and diameter

Example of identified rocks (point features)

Example of identified boulders (polyline features)

Rock and Boulder Locations Small bodies, like asteroids, “are often

irregularly shaped with regions that cannot

be uniquely addressed with longitude and

latitude” (DellaGiustina, et al., 2017, page 1)

◦ Identification of hazards is not relevant to

sample-site selection until mapped to the

body-fixed XYZ coordinates of the asteroid’s

3D shape model

Asteroid Bennu at 80 km distance Asteroid image © NASA/Goddard/University of Arizona

X

Y

Z

~500 m

Body-fixed XYZ Coordinates Image used to identify rocks and boulders is one band of a composite

band raster dataset

◦ Raster is output from United States Geological Survey’s (USGS’s) Integrated

Software for Imagers and Spectrometers 3 (ISIS3)

◦ ISIS3 can project a complex-shaped 3D body’s surface, and corresponding

attribute values, into a 2D composite band raster dataset: a “backplane”

ISIS3 composite band raster dataset (“backplane“)

Image © United States Geological Survey

Rock

Extracting the values from

the backplane (raster

bands) for the rock and

boulder locations, provides

geometric coordinates.

Low

High

Process of Coordinate Extraction Existing process used by OSIRIS-REx Image Processing Working Group (IPWG)

◦ Manual; many steps where human error could be introduced

This Master’s Project automates the workflow of body-fixed coordinate extraction from an ISIS3 backplane

◦ Interviewed mission’s Image Processing Engineer

◦ Gathered task requirements, inputs, mathematical formulas for error-checking, and required outputs

◦ Developed an Esri ArcMap™ Python Toolbox Tool

◦ 650 lines of code / 20 Esri ArcPy functions

Image © esri: Python Toolbox

Test Data Used During Development During this project’s development, the OSIRIS-REx spacecraft was still en

route to Bennu and available imagery not yet high-resolution enough for

identifying rocks and boulders

◦ Used test data of comet 67P/Churyumov–Gerasimenko from European

Space Agency’s (ESA’s) Rosetta mission as projected by ISIS3

~4 km 920 m

Comet 67P/Churyumov–Gerasimenko

Image © ESA/Rosetta

Outline Methods

◦ User parameters and input validation

◦ Workflow steps

Results

◦ Graphical user interface

◦ Status output and warning/error messages

◦ Shapefile output

Conclusion

References

Methods WALKING THROUGH THE WORKFLOW

Comet 67P/Churyumov/Gerasimenko

Shapefile Input(s)

Point or Polyline Features? Polyline Point

ISIS3 Raster Dataset

Temporary Geodatabase

Isolate Raster Bands

Clip Features to Match Raster

Preserve Shapefile FIDs

Convert Polylines to Start, Mid, End

Vertices

Extract Geometry Information from

ISIS3 Raster

Body - fixed XYZ

Coordinates

Projected Latitude / Longitude

Calculate Latitude/ Longitude

Log Output of Feature Errors

Join Points · New Attributes with

Original Polylines

Export Final Shapefiles


ISIS3 Raster

Body - fixed XYZ

Coordinates




Input Validation


User Parameters and Input Validation

Required User Parameters:

◦ Point and/or polyline shapefile(s)

◦ Corresponding ISIS3 raster backplane (.CUB file)

◦ Four band minimum (image + XYZ bands)

◦ Output folder

Esri ArcMap™ Licensing Validation

◦ Available 3D Analyst & Spatial Analyst licenses

◦ Licenses are automatically checked in/out during

workflow processing

Shapefile Input(s)








Vertices


ISIS3 Raster

Body - fixed XYZ

Coordinates





Original Polylines



ISIS3 Raster

Body - fixed XYZ

Coordinates




Input Validation


User Parameters and Input Validation

Optional Latitude/Longitude Test

◦ Compares calculated latitude/longitude to

projected latitude/longitude for error-checking

◦ Latitude/longitude formulas are from OSIRIS-REx

Image Processing Engineer, Carina Bennett

◦ Any extraction that is beyond user-defined threshold

is written to text file log

◦ ISIS3 backplane must contain projected latitude &

longitude raster bands

Shapefile Input(s)








Vertices


ISIS3 Raster

Body - fixed XYZ

Coordinates





Original Polylines



ISIS3 Raster

Body - fixed XYZ

Coordinates




Input Validation


Creation of Temporary Geodatabase

Input shapefiles are imported into a temporary

geodatabase as feature classes

◦ Re-created each time Tool is used

◦ Workflow processing occurs within geodatabase

◦ Some ArcPy functions don’t take shapefiles as inputs

◦ More organized for handling interim feature classes

◦ After all processing, final output will be time-

stamped shapefiles in user-defined directory

Shapefile Input(s)








Vertices


ISIS3 Raster

Body - fixed XYZ

Coordinates





Original Polylines



ISIS3 Raster

Body - fixed XYZ

Coordinates




Input Validation


Isolation of Raster Bands ISIS3 backplane bands isolated for processing

◦ Last three bands in raster dataset are used as XYZ

bands, per ISIS3 format specification

◦ Optionally, if user selected latitude/longitude

bands, those will also be isolated

◦ Latitude/longitude band indices aren’t fixed

◦ Used for the optional Latitude/Longitude Test

Shapefile Input(s)

Point or Polyline Features?

Polyline Point







Vertices


ISIS3 Raster

Body-fixed XYZ

Coordinates



Log Output: Feature Errors

Join Points’ New Attributes with

Original Polylines

Input Validation


Preserving of Shapefile FID Shapefiles were imported as feature classes, and

will be clipped in upcoming step

◦ Feature class OBJECTIDs will start at 1, but

shapefile Feature IDs (FIDs) start at 0

◦ Clipping features to the raster footprint will also

re-order the OBJECTIDs

Important to preserve the original IDs of the

features for joining functions

◦ “SHP_FID” field is created in feature class and

preserves data integrity throughout processing


Polyline Point





Vertices


ISIS3 Raster

Body-fixed XYZ

Coordinates





Original Polylines


Clipping of Features to Raster Footprint

During user-identification of rocks and boulders,

point and polyline features could be “drawn”

outside bounds of ISIS3 backplane raster

◦ Would result in extraction of problematic NULL

values for those features

Footprint is calculated for raster and used to clip

features that extend outside its limits

◦ Shapefile FID is preserved

◦ “3D Analyst” license required for Raster Domain

geoprocessing


Polyline Point





Vertices


ISIS3 Raster

Body-fixed XYZ

Coordinates

Projected Latitude /

Longitude




Original Polylines


Accounting for Polylines Coordinates will be extracted from backplane for

points, but boulders are recorded as polylines

◦ Additional processing steps needed for boulders

◦ Not needed for rocks: are already point features

◦ For sake of presentation, will assume processing

of boulder features


Vertices


ISIS3 Raster

Body-fixed XYZ

Coordinates


Longitude




Original Polylines


Conversion of Polylines to Point Features

Boulders’ polyline features are converted to

start, middle, and end vertices

◦ Allows for extraction of ISIS3 backplane body-

fixed XYZ coordinates for boulders

◦ Stored in interim-workflow feature classes

Illustration of polyline-to-point conversion


Vertices


ISIS3 Raster

Body-fixed XYZ

Coordinates


Longitude




Original Polylines


Extraction of Body-Fixed Geometry At this point in the workflow:

◦ Rock and boulder shapefiles were imported into the temporary geodatabase

◦ Shapefile FIDs were preserved

◦ ISIS3 backplane raster bands, containing geometric attributes, were isolated

◦ Features outside of raster’s footprint were clipped

◦ Polyline-features were converted to start, middle, and end point-features

Extraction of body-fixed XYZ coordinates, and optional latitude/longitude, can now occur.


Vertices


ISIS3 Raster

Body-fixed XYZ

Coordinates


Longitude




Original Polylines


Extraction of Body-Fixed Geometry Asteroid body-fixed coordinates are extracted for each feature in the input shapefiles ◦ For rocks, attributes are extracted for a single

point

◦ For boulders, attributes are extracted for the start, middle, and end points of the original polylines

◦ “Spatial Analyst” license required for Extract Multi-Values to Points geoprocessing

ISIS3 composite band raster dataset (“backplane“)


Vertices


ISIS3 Raster

Body-fixed XYZ

Coordinates


Longitude




Original Polylines


Calculation of Latitude/Longitude

Using the extracted body-fixed XYZ coordinates,

the latitude/longitude of the features are

calculated and stored as attribute data

◦ Formulas provided by OSIRIS-REx Image

Processing Engineer, Carina Bennett, in SQL

◦ After converting them to Python, they are:

Formula in Python

Lat. math.asin(z / (math.sqrt((x)**2 + (y)**2 + (z)**2))) * 180 /

math.pi

Lon. math.atan2(y, x) * 180 / math.pi - math.floor((math.atan2(y,

x) * 180 / math.pi) / 360) * 360 Original formulas were provided in SQL by OSIRIS-REx Image Processing Engineer, Carina Bennett


Vertices


ISIS3 Raster

Body-fixed XYZ

Coordinates


Longitude




Original Polylines


Joining of Data to Original Polylines

Polyline boulder features were converted to

point features, meaning that:

◦ Boulders’ coordinate extractions took place in

interim-workflow feature classes

◦ Preserved, original shapefile FID is key for join to

occur correctly

◦ Rock point-features do not need joining;

coordinates were extracted directly to points




Original Polylines


Logging of Errors from Lat/Lon Test

Optional test occurs if user provided band

indices for latitude/longitude

◦ Calculated latitude/longitude is subtracted from

the extracted, projected latitude/longitude

◦ Delta is compared to user-defined threshold

◦ Any feature that is outside threshold is written to

a time-stamped text file with the feature’s ID #

◦ Warning message is also posted to ArcMap™’s

geoprocessing results




Original Polylines


Exporting of Final Shapefile Output Attribute data of rock and boulder feature classes, processed inside the temporary geodatabase, now contain asteroid body-fixed:

◦ X-, Y-, and Z-coordinates

◦ Calculated latitude & longitude coordinates

◦ Optional projected latitude & longitude coordinates

Feature classes are exported as time-stamped shapefiles to user-defined output directory

◦ Optional Latitude/Longitude Test results will also be written here and to ArcMap™’s geoprocessing results

Results USER INTERFACE, STATUS MESSAGES, & SHAPEFILE OUTPUT

Results: Graphical User Interface

Status Output and Warning/Error Messages

Shapefile Output: New Attribute Data

Shapefile Output: Why Use Shapefiles? Shapefiles are the required output:

◦ Natively recognized by computer filesystems

◦ More easily programmatically-accessed by scientists’ algorithms and tools

than feature classes in a geodatabase

Output shapefiles are used in further processing by the OSIRIS-REx

Image Processing Working Group to derive higher-level data products.

Locations of rocks and boulders will ultimately reside in the mission’s

Hazard Geodatabase to aid in selection of Bennu’s sample-site

◦ One of many inputs to the mission’s Sampleability and Science Value maps

Conclusion MISSION ACCOMPLISHED

Conclusion “OSIRIS-REx is unique among planetary missions in that all remote sensing is performed to support the sample return objective.” (DellaGiustina, et al., 2016, page 1)

Critical that OSIRIS-REx scientists know the asteroid 3D body-fixed XYZ locations of hazardous features on Bennu to determine sample-site.

Locating hazards in body-fixed coordinates achieved through unique methods:

◦ USGS ISIS3 software projects a composite band raster dataset that contains the body-fixed geometry information

◦ Extraction of these data to identified geographic features

Image © University of Arizona Image © United States Geological Survey

Image © esri

Conclusion This Master’s Project ArcMap™ Python Toolbox Tool provides:

◦ Automation of USGS ISIS3 backplane values extraction for input

features’ locations;

◦ Employs a graphical user interface (GUI), error-trapping, input

validation, logfile output, in-line help message dialog;

◦ Customizable user-defined inputs and outputs.

Image © University of Arizona Image © United States Geological Survey

Image © esri

Special thanks to: Carina Bennett, OSIRIS-REx, USGS, Esri, and Dr. Chris Lukinbeal THANK YOU!

References WORKS CITED

References D. N. DellaGiustina, O. S. Barnouin, M. C. Nolan, C. A. Johnson, L. Le Corre and D. S. Lauretta; Lunar and Planetary Laboratory,

University of Arizona, Tucson, AZ; The Johns Hopkins University Applied Physics Laboratory, Laurel, MD; Planetary Science

Institute, Tucson, AZ.

◦ 2016. Cartographic Planning for the OSIRIS-REx Asteroid Sample Return Mission.

D.S. Lauretta, S.S. Balram-Knutson, E. Beshore, W.V. Boynton, C. Drouet d’Aubigny, D.N. DellaGiustina, H.L. Enos, D.R. Golish,

C.W. Hergenrother, E.S. Howell, C.A. Bennett, E.T. Morton, M.C. Nolan, B. Rizk, H.L. Roper, A.E. Bartels, B.J. Bos, J.P. Dworkin, D.E.

Highsmith, D.A. Lorenz, L.F. Lim, R. Mink, M.C. Moreau, J.A. Nuth, D.C. Reuter, A.A. Simon, E.B. Bierhaus, B.H. Bryan, R. Ballouz,

O.S. Barnouin, R.P. Binzel, W.F. Bottke, V.E. Hamilton, K.J. Walsh, S.R. Chesley, P.R. Christensen, B.E. Clark, H.C. Connolly, M.K.

Crombie, M.G. Daly, J.P. Emery, T.J. McCoy, J.W. McMahon, D.J. Scheeres, S. Messenger, K. Nakamura-Messenger, K. Righter, S.A.

Sandford.

◦ 2017. OSIRIS-REx: Sample Return from Asteroid (101955) Bennu.

D. N. DellaGiustina, C. A. Bennett, D. R. Golish and N. Habib; Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ.

◦ 2017. Generating Photomosaics of Small Bodies in Preparation for the OSIRIS-REx Encounter with Asteroid Bennu.

All images copyright of their respective owners: citations are in-line and appear next to images.

Space Rocks! A Python Toolbox Tool for Asteroid Hazards' Body-Fixed Coordinate Extraction · 2019....

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Transcript of Space Rocks! A Python Toolbox Tool for Asteroid Hazards' Body-Fixed Coordinate Extraction · 2019....