Author:
Keith Tyser
San Diego State University
Co-Authors:
Cameron Williams

Abstract

There are many challenges involved in conducting optimal aerial insertions and freefall operations. Difficulties measuring atmospheric conditions “through the wind column” and characterizing the maritime environment along with many other environmental variables exposes operators to a higher level of risk than necessary. Our solution, Full Aerial, utilizes various sensors already standard to aircraft along with lidar technology, creating a fusion of information that helps operators characterize the atmospheric conditions and maritime environment in real time.

Problem Statement

The amount of data and information operators have about their environment when conducting aerial operations can be limited, making it challenging to select landing spots with minimal risk. Devise a system which can be employed in-flight by large fixed-wing aircraft to measure, record, and display atmospheric data through the wind column. The system should be capable of operating during daytime or nighttime. Ideally, the system can return information to operators in real-time, over a designated area roughly straight below the aircraft (does not need to work outside a narrow vertical cylinder). A second system, either integrated or independent, should be capable of measuring, recording, and displaying information about the sea state. This includes wave height at a minimum, and additional attributes are welcome.

 

Proposal

Full Aerial is a sensor fusion system that we plan to design with the following functions at a minimum:

  • Measuring wind speed - We plan on utilizing lidar technology to measure the ground speed and an anemometer to measure air speed, which will allow us to calculate wind speed relative to the ground through the wind column
  • Measuring wind direction - We will utilize an anemometer to determine the wind direction
  • Measuring wave characteristics - We will utilize lidar technology to directly measure wave profiles and properties (e.g. wave height and period) with a goal of characterizing the sea state for operators and producing three dimensional renders
  • Real-time graphical user interface - Our system will display the information collected from our sensors in an easy-to-understand GUI for operators to make decisions in real-time

Additionally in the future, we would like to add object detection capabilities and the ability to characterize the slope of landing zones. 

The hardware for our system will consist of a Raspberry Pi 4 Model B as the main computer to run scripts, perform calculations, and drive our fusion of sensors. Our system will use lidar sensors and anemometers for atmospheric and environmental measurements, and it will also utilize an electro-optical camera and RF radar shield to mirror technologies standard to military aircraft. We will use a high level programming language to be decided later that will run the backend operations of our system. In total, the hardware budget needed in order to create our minimum viable product is ~$800. 

To test our proposed solution we plan to mount our system to the chassis of a remote-controlled drone. This will allow us to validate the environmental and atmospheric measurements of our system in a simplified test environment while still mirroring flight conditions. A durable drone with the capability of flying at a high altitude costs within range of ~$300-$1500. 

 

Challenges and Unknowns

  • Special clearance is required to fly drones above 400 feet. If we need to fly above 400 feet and aren’t able to gain that permission it could impact the testing and validation of our system.
  • We need to design a way to properly protect and secure our system to a drone so it can withstand environmental conditions.
  • Clouds and harsh weather conditions may have a currently undetermined impact on the accuracy of our sensors.
  • There are some complex mathematics and physics involved with this, which always leaves room for human error.
  • Prototype level sensors compatible with a raspberry pi have limited functionality and range compared to full capability sensors that would be used on aircraft.

Sources

https://www.researchgate.net/publication/331345622_Mapping_Ocean_Waves_using_LIDAR_Technology

https://www.hindawi.com/journals/js/2016/7965431/

https://onepetro.org/ISOPEIOPEC/proceedings-abstract/ISOPE19/All-ISOPE19/ISOPE-I-19-318/21405

https://journals.ametsoc.org/view/journals/atot/23/11/jtech1936_1.xml

 

Comments

dBlocher | 12 February 2021

I'm excited to see your proposal - this is a challenging problem and a great idea. It's great to see that you did a bit of poking around to see what technologies are out there. Here's the first 2 things that came to mind for me:

First of all, as you mentioned clouds would have a large impact on ground looking airborne sensor. It depends on the altitude of the platform, region of the globe (typically worse in PACOM than CENTCOM) and time of year. Here's a link to help give a sense of cloudiness:

https://earthobservatory.nasa.gov/global-maps/MODAL2_M_CLD_FR

In a ray from space to earth you'll often hit a cloud, and those clouds will typically form in the the ~1,000-40,000 ft range, so an aerial insertion from 30,000 ft would typically be in or above the clouds. Though certainly the platform could descend below the cloud base for insertion.  You could always reach out to a contact in the operational community here to get a gut check. It may be that they need something that works for high-altitude insertion above a cloud deck, or it may be that they never jump through clouds so this is a non-issue. The articles that you found which used LiDAR to map wave heights appear to all be surface sensors which sit below the cloud deck so wouldn't have this issue.

The second thing to consider would be variation of wind within the column. As you point out, by measuring ground speed and air-speed you can infer wind-speed at the platform. However, the wind gradient/sheer could be quite high such that atmospheric profile that a jumper encounters below the aircraft is quite different than the winds at the aircraft. In addition, for a platform deciding whether it is safe for it to descend, it is that shear which would likely be the relevant thing to measure. The LiDAR sensor you propose could be used to profile the wind column by jettisoning something and tracking it's decent through the column. Here, I think the question is whether use of an expendable item would be acceptable from a mission perspective. A quick analysis you could do there is estimate the profile of a body falling through vertical or horizontal shear wind, compare that with the angular resolution of your system. Another option with LiDAR would be a Doppler LiDAR where light that is scattered by the air is measured (rather than a hard target such as terrain). Here's a link:  https://www.arm.gov/publications/tech_reports/handbooks/dl_handbook.pdf  You'll see the impact of clouds in some of their ground looking up data.

 

 

-david

anthony.ingano… | 12 February 2021

I like the idea of dropping a sensor from the aircraft. I'm not sure of how quickly the data can be retrieved and analyzed in real-time, though. Seems like some of the technology already exists with hurricane hunters that go through storms and drop canisters to improve the forecast .   I would think you could get wind conditions plus maybe wave conditions all within the same canister.

achang7 | 12 February 2021

Keith, my direct experience is with static line operations, but I have worked closely with folks executing free fall operations. From an altitude and cloud cover perspective, generally, static line operations take place from 800 ft AGL to 1,500 ft AGL and normally below cloud cover. There are combat exceptions that allow you to jump from 500 ft AGL. On the free fall side of the house, jump altitudes are typically between 3,500 ft AGL and 25,000 ft AGL. Conducting free fall operations through cloud cover is not uncommon, though there must be some altitude breaks in the clouds to allow jumpers to safely exit the aircraft and assemble under canopy. Typically 1,000 ft gaps are used.

The SOF communities associated with the SOCOM Ignite project will be most interested in free fall operations. However, a proof of concept given your current limitations with altitude and visibility would still be extremely valuable. Static line operations are still a tool in the tool chest and many free fall operations take place with at least intermittent cloud cover that would allow at least brief windows for your LIDAR-based system to work. Also, when conducting free fall with large equipment bundles, those operations tend to take place on the lower side of the altitude scale. It sounds like you are already pursuing it, but certainly seeking the altitude waiver for your drone would be advised.