Embedded Files
January 2024
Mars 2020: Nailing the Landing
Mars 2020: Nailing the Landing
Sitting within the Insidis Planitia region of mars, where an ancient impact left behind a basin some 750 miles across, Jezero Crater is the result of a repeat impact within the Insidis impact basin. Past missions to mars have revealed that it was once the site of a lake thanks to the discovery of clays at the site which can only form in the presence of water. Scientists believe that the crater could've been habitable in the distant past due to similarities that the rock itself has to features found here on Earth. The Mars Perseverance Landing Site covers the upper middle portion of the Jezero Crater, and the mission set out to make mosaics of several areas, including the much smaller impact site of Belva Crater. Alongside the Perseverance rover, however, was the Ingenuity Mars Helicopter, a hitchhiker by mission standards, but a trailblazer for extraplanetary powered flight.
Credits: ESA/DLR/FU-Berlin/NASA/JPL-Caltech
The First of Many
The First of Many
In April of 2021, Ingenuity became the first aircraft to achieve self propelled autonomous flight on another planet. Nicknamed Ginny, the helicopter completed 72 flights in its three years of operation, far exceeding its designed capabilities, and opening up a world of possibilities for future missions to our planetary neighbors. Despite being designed solely as a demonstration of the technology; it doesn't put a damper on imagination. We have a limited amount of images captured by Ingenuity, but we have more than enough data to replicate what it saw.
Click (or touch) and drag to interact with this 3D model of the Mars 2020 Ingenuity Helicopter. Credits: NASA/JPL-Caltech
Can a Viewshed Analysis on ArcGIS Pro accurately replicate what Ingenuity saw on Mars?
First Steps: Data Acquisition & Preparation
First Steps: Data Acquisition & Preparation
A digital terrain model (DTM) covering the Mars 2020 landing site at Jezero Crater was acquired from Astropedia, a lunar and planetary cartographic catalog housed by the USGS Astrogeology Science Center. The DTM is an orthorectified image mosaic made by the Jet Propulsion Laboratory at NASA with HiRISE data following a standard USGS process for generating HiRISE DTMs specifically for surface operations and mapping. This mosaic was picked over other available DTMs because of its detail clarity, but also because of its direct association to the Mars 2020 mission, making it the most suitable candidate for this analysis. To make the final product look more interesting, an HCM30 Color Base Map was acquired from the German Aerospace Center to add color to the hillshade, and nomenclature layers from a Geologic Map of Jezero Crater and the Nili Planum Region was used to label Belva Crater.
Additionally, Ingenuity Helicopter Waypoint data and Helicopter Flight Path data were acquired from the Perseverance Rover Location live map, and Ingenuity's flight log was copied into a Microsoft Excel sheet from the Mars Helicopter Tech Demo site, both of which are hosted by NASA. Finally, documentation about Ingenuity's on-board cameras was sourced from a Mars Helicopter Technology demonstrator published by the Jet Propulsion Laboratory, the NASA Ames Research Center, and CALTECH. This data would be used to determine variables important to the viewshed toolset in ArcGIS Pro.
Acquired data layers overlayed with the helicopter waypoints.
Additionally, the projected helicopter waypoints layer was copied, since visibility attributes would be added to the table of the waypoints layer, and it's good practice to keep original data intact. ArcGIS tools for viewshed analysis can use several input parameters, so that each observer point can be determined by a different set of conditions.
For this analysis, it was important to ensure that Ingenuity's field of view with its navigation camera could be replicated. The FOV of Ingenuity's NavCam was used to preserve authenticity, as that was the main camera onboard the helicopter and it's also the one that returned images of the Martian surface to scientists on Earth.
Once the required data layers for the viewshed analysis were acquired, the layers were all projected to the Equirectangular Mars 2000 sphere IAU projection using the Project tool, which corrected a slight misalignment between the DTM and the Color Base Map. A shapefile was made to create a smaller extent for the data to make loading and visualizing the data in 3D scenes easier. That shapefile was then edited to create an even smaller area, which would serve as the actual study area.
Cropped area with study area shape layer overlayed. Helicopter waypoints and Belva nomenclature added for spatial reference.
Visual representation of the variables used by the Viewshed tool with respect to Ingenuity's NavCam FOV.
Ingenuity's NavCam was pointed downwards and had a field of view of 133°(horizontal) by 100°(vertical). To account for this in the viewshed analysis, the vertical angle variables VERT1 and VERT2 were set to -45° and -90°, numbers that correlate to the horizontal plane equalling 0 and numbers below the plane being negative. Since VERT1 and VERT2 have a maximum of -90, the numbers were converted to -45 and-90 as the closest estimate of the field of view.
Flight Log data was painstakingly copied into Excel, where minimum, average and maximum flight altitudes (m) were calculated using built in functions. These would be used as OFFSETA values. In ArcGIS Pro, OFFSETA is used as a variable for viewshed analysis that adds height to an observation point. Since the waypoints were not taken "in the air," it was important to ensure that the viewshed was calculated from above ground level.
The Add Fields (Multiple) tool was used to add the fields onto the Helicopter Waypoint data for the OFFSETA, VERT1, VERT2, and RADIUS2 variables. Then, the Calculate Field tool was used to fill them with the specified values (10.63, -45, -90, 34 respectively).
Part Two: Viewshed Analysis, Optimization and Results
Part Two: Viewshed Analysis, Optimization and Results
Once all of the required data for the analysis had been processed, the Viewshed (Spatial Analyst) tool was used to determine the raster surface locations visible to the Ingenuity Helicopter on each of its waypoints. The Input Raster was set to the projected DTM, and the Observation Points were set to the projected Helicopter Waypoints. It wasn't necessary to adjust the z value, nor was it necessary. With a scanning range of 24 meters, the points were small compared to the rest of the data, but it was still possible to reference them with images taken by the NavCam. Some changes that were made to the data after evaluating the results of the viewshed was increasing the VERT1 variable to 0 as opposed to keeping it at -45°. This was done because review of the technical documents relating to Ingenuity's construction revealed that the cameras were actually installed with an offset. Additionally, the RADIUS2 variable was increased from 24m to 30m, as when the viewshed results were being cross-referenced with actual imagery that Ingenuity took, the Perseverance rover was pictured where the viewshed analysis didn't reach despite being under 24m. The RADIUS2 parameter was changed instead of the OFFSETA to avoid having multiple viewsheds with conflicting vertical references. I really wanted to keep the analysis with the average altitude of the flights, as opposed to going for altitudes that might be unrealistic. Finally, another study area was refined to make running the newer viewsheds faster, since the fine resolution of the DTM made the Viewshed tool take quite a while.
Ingenuity Camera Setup. Credit: JPL, CALTECH, NASA Ames Research Center
Ingenuity Captures Perseverance at Belva Crater. This image was used to show that Perseverance would've been visible for Flight 50 too. Credit: NASA/JPL-Caltech
With all of these changes, the resulting viewshed covers 149,375 cells, but with the resolution of the underlying raster being 1m, that's a total of 149,375 meters that Ingenuity could see if it was hovering at an altitude of 10.63m at each waypoint.
Final Viewshed Attribute Table
Final Viewshed of Helicopter Waypoint Data
To really put Ingenuity's viewshed to the test, another viewshed analysis was performed, this time using Ingenuity's flight path data as opposed to the waypoints. Since the Viewshed tool cannot use lines, the Helicopter Flightpath data was turned into point data using the Create Point Features Along Line tool. Points were spaced 10m apart, and finishing points were added at the start and end of the line. The viewshed was calculated with the same OFFSETA, VERT1, VERT2 AND RADIUS2 parameters as the final viewshed of the helicopter waypoint data.
The resulting viewshed covers a whopping 308,729 cells, and more accurately accomplishes what the project set out to do. As a final proof of concept to show that the viewshed is accurate, several pictures taken by Ingenuity's cameras were compared to the resulting viewshed. To do this, the study area was rendered into a 3D Local Scene in ArcGIS Pro. Rendering the surface of Mars as accurately as possible while having a relatively low resolution color basemap was challenging! I got the best results when I set the color raster to 32% transparency and used the Multiply layer blend. Additionally, I used a Cubic resampling type for both my DTM and color raster, and set the color raster's layer gamma to 1.0.
'Fortun Ridge' visible on a Render of Flight 27's Viewshed (albeit, very grainy!)
'Fortun Ridge' Imaged on Ingenuity's Flight 27 Credit: NASA/JPL-Caltech
Despite not being able to recreate everything accurately due to the Viewshed's parameters (and grainy color basemaps), it's exciting to see that we can simulate these scenes on ArcGIS Pro!
Ingenuity Captures Perseverance at Belva Crater (Arrow points to Perseverance Rover) Credit: NASA/JPL-Caltech
Render of Ingenuity's 51st flight at Belva Crater with an in-engine altitude of 12m to match the actual flight altitude, which places Perseverance outside of the viewshed's parameters.
Ingenuity's View of Sand Dunes During Flight 70, at an altitude of 12m, which is beyond the viewshed's field of view but still visible to it! Credit: NASA/JPL-Caltech
Rendering of Ingenuity's Viewshed of Sand Dunes During Flight 70, at an altitude of 12m, which is beyond the viewshed's field of view but still visible to it!
Finally, this is what the Viewsheds look like rendered into a 3D scene.
3D rendering of Ingenuity's flight path with the viewsheds calculated from the helicopter's waypoint data. (Above)
3D rendering of Ingenuity's flight path viewshed. (Above)
All in all, Ingenuity saw Mars like never before. I cannot wait to see what our next helicopter on Mars is going to be equipped with! Check out the Mars Science Helicopter here, which will be NASA's next iteration of the mars helicopter concept. Designing an imaging instrument is only half the battle, and I think that the field of Planetary GIS is going to be booming in the next few decades. I cannot wait to be a part of it.
Sources
Sources
Data
Mars 2020 Terrain Relative Navigation HiRISE DTM Mosaic, USGS Astrogeology Science Center, Available at https://doi.org/10.5066/P9REJ9JN 2020.
Sun, Vivian. Stack, Kathryn M. Geologic Map of Jezero Crater and the Nili Planum Region, Mars [map]. Scale Not Given. USGS Astrogeology Science Center. Available at https://doi.org/10.3133/sim3464 2020.
HRSC MArs Chart (HMC-30) Pansharpened RGB Color Mosaic– HMC_13E14_co5, Institute of Planetary Research, German Aerospace Center, Available at https://hrscteam.dlr.de/public/data/HMC30/quads.php?quad=mc13e
Perseverance's Location, NASA. Available at https://mars.nasa.gov/maps/location/?mission=M20
Balaram, J (Bob). et al. Mars Helicopter Technology Demonstrator. Jet Propulsion Laboratory, California Institute of Technology, NASA Ames Research Center. 2018 AIAA Atmospheric Flight Mechanics Conference. Available at https://doi.org/10.2514/6.2018-0023, but for free at https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_AIAA2018_0023.pdf
SONY IMX 214 Product Brief. Mouser, Available at: https://www.mouser.com/datasheet/2/897/ProductBrief_IMX214_20150428-1289331.pdf
OV7251 VGA Product Brief, OMNIVISION, Available at https://www.ovt.com/products/ov7251/
Mars Ingenuity Helicopter, 3D Model, NASA Science MARS Exploration, Available at https://mars.nasa.gov/resources/25043/mars-ingenuity-helicopter-3d-model/
Images from the Mars Helicopter, NASA Science MARS Exploration, Available at:
https://mars.nasa.gov/resources/26707/fortun-ridge-imaged-on-ingenuitys-flight-27/
https://mars.nasa.gov/resources/27429/ingenuity-captures-perseverance-at-belva-crater/
https://mars.nasa.gov/resources/27901/ingenuitys-view-of-sand-dunes-during-flight-70/
MARS Helicopter Tech Demo, NASA SCience, "Flight Log" and "Helicopter Highlights" Accessed. Available at https://mars.nasa.gov/technology/helicopter/#
Perseverance Rover's Landing Site: Jezero Crater, MARS 2020 Mission Perseverance Rover, NASA Science. Available at https://mars.nasa.gov/mars2020/mission/science/landing-site/
For those curious, here's a copy of the Flight Log data for Ingenuity! Pulled this straight from the mission website. The functions I used for my calculations aren't available on this sheet, since it's just a copy paste from an excel sheet, but they're just avg/min/max!
Page updated
Google Sites
Report abuse