Recipient Organization
NEAR SPACE LABS INC
141 FLUSHING AVE
BROOKLYN,NY 11205
Performing Department
(N/A)
Non Technical Summary
In the face of the rising climatic threats, access to well-adjusted housing insurance is a must. Modern insurance carriers heavily rely on aerial imaging of properties and AI models, to quote and assess premiums at the renewal time, and to pay out damages upon claims after events like hurricanes or winter storms. Up-to-date aerial imaging is necessary before and after damage events, as it helps speed up payouts and adjust and quote insurance premiums at a more competitive rate.However, the updated aerial imaging necessary to extend this improvement and resiliency to rural areas is missing. Typically, this imaging is captured with airplanes at a 2-4 inch/pixel resolution, but does not cover US rural areas due to cost and scalability issues. It is estimated that 60M rural properties are missing updated imagery.In order to bridge this gap, we propose the usage of stratospheric balloons to provide high resolution imaging. Balloons at 60,000 ft and higher provide a vantage point from which imaging large rural areas at the reasonable cost becomes feasible. The key technological development needed is an optical system capable of achieving the necessary resolution from stratospheric heights. In this project, we design, prototype and test such an optical system. We expect to achieve a lightweight telescope design capable of enduring a low-temperature, low-pressure environment and providing 2-4 inch resolution imaging from the stratosphere.
Animal Health Component
20%
Research Effort Categories
Basic
(N/A)
Applied
20%
Developmental
80%
Goals / Objectives
The overall goal of this project aims to reach a proof of concept (POC) of a high-altitude imaging system for high-resolution imaging of rural areas at Technology Readiness Level (TRL) 6, with a resolution as specified by the project's GSD requirement. This breaks down further into 7 objectives, each with questions to be addressed in their respective work packages. Note that from now on, we interchangeably use the term 'payload' and 'imaging system'.Objective 1: Generate a full set of payload specifications, guided by end user requirements within the constraints of our flight vehicles and operation conditions.What is the minimum flight altitude and field of view required to make operations with this payload viable?What is the maximum mass and volume budget within the constraints of our flight vehicle?What design will provide the required optical performance (e.g. focal length, f-number, contrast) within these constraints?What temperature dynamics and mechanical shocks is the payload subjected to during an operational cycle of launching, flight and landing?Objective 2: Optical and mechanical design of the imaging payload to fulfill the imaging specifications, choice of a suitable image sensor and a mechanical mounting scheme for flight vehicle integration.What type of optical design (telescope type, refractor, reflector, catadioptric) will provide the required performance within a tight mass budget and which COTS image sensors are best suited to match this design?What mechanical design and materials will ensure the system performs under stratospheric conditions, and over many cycles of launching and landing?Will this design require unconventional manufacturing techniques, e.g. mirror lightweighting?How does the stabilization mechanism in our flight vehicles need to be modified to accommodate for this payload?Objective 3: Optical and mechanical component manufacturing. Supplier identification, manufacturing and purchasing of materials and equipment.Can a single supplier manufacture the different types of optical components (e.g. mirrors, lenses) potentially required?If necessary, can they provide specialized manufacturing techniques (e.g. complex shapes, optical coatings)?Do they have suitable testing means to inspect the components?Objective 4: Design and assembly of an optical test bench to verify system performance in the lab.Which optical testing scheme is most efficient to quickly reach and confirm the payload's optimal performance over the full field of view?How can we make sure the sensitivity test bench is sufficient for testing the payload?Objective 5: Prototype AIT demonstrating optical performance in the lab.Does the payload provide the optical performance required in a lab setting?If not, what causes this?Objective 6: Lab testing of payload resilience against mechanical shocks.What is an efficient method to simulate landing shock in the lab?To what degree is payload performance affected by landing shock?If so, is the performance degradation within the tolerances?Objective 7: Environmental testing under realistic conditions.What is the most time and cost effective solution to test imaging performance under realistic conditions?How much, if at all, does payload performance degrade under these conditions and what causes this?
Project Methods
WP1: The goal of this first work package is to determine a full set of payload specifications to ensure that end-user requirements are met within a mass and volume budget defined by our flight vehicle, while also taking into account operational constraints that make the use of the payload economically viable. To image enough area per flight to make operations economically viable and provide cost-effective imaging, the payload needs to be flown at an altitude of above 60,000 ft and provide a field of view of at least 2º diagonal. Combined with the end-user specification of 2-4 in/pixel ground sampling distance (GSD), these values provide a framework to guide optical design, for instance to determine their required f-number and to define a matching optical resolution and modulation transfer function (MTF) criterion for subsequent performance evaluation [14]. Volume and mass limitations for NSL's flight vehicles dictate a maximum payload mass of 3.3lb. From previous flights where we recorded temperature and accelerations of the payload bay throughout the flight, we obtained statistics that determine the range of temperatures and mechanical shocks that the payload must sustain during typical flight operations.WP2: The optical engineering team will start this work package with a trade study of different optical telescope designs for the imaging optics that fulfill the specifications derived during WP1. Here, the criteria will be to select a design requiring the minimum number of elements while delivering wide-field performance, and we will focus on proven designs used in the EO satellite community, for instance, Ritchey-Chretien telescopes [15], [16]. This step also entails selecting a suitable COTS image sensor compatible with those requirements. Once a suitable combination of telescope design and image sensor is determined, we will perform optical system design, simulation and optimisation using modeling software (Zemax OpticStudio) to ensure performance, based e.g. on the resolution criterion defined in WP1 and manufacturability, including tolerances for realistic manufacturing. Once completed, our mechanical engineering team will proceed with the design of a lightweight, robust and accurate mounting system for the optics, including the selection of suitable materials for the mount and optical components to make the system as immune as possible to environmental influences.?WP3: In this work package, we will identify and verify suitable optics and metalwork suppliers immediately after completion of the payload design to mitigate potential supply chain issues and delays in manufacturing. If the design comprises different types of elements, this may entail finding different suppliers for each component. Nonetheless, all potential suppliers need to be vetted for manufacturing and testing capabilities, particularly for the optical components that will likely have complex shapes and need to be tested on site by the manufacturer to quickly react to potential defects and fabrication errors. In parallel, we will also order the image sensor in this WP to ensure that it arrives in time for assembly.WP4: In this work package, the optical engineering team will design a suitable testing scheme to confirm the optical performance of the payload in the lab. First, we will select a testing method that enables reliable, quantitative and fast payload alignment and performance evaluation. Here, again, we focus on test schemes proven in the EO community, including resolution target tests [17], measurement of the MTF [18] or interferometric testing [19]. Once selected, we will build a benchtop optical setup implementing this test using COTS components, similar to the example shown in Fig. 4a. To confirm the capabilities of our setup, we will test it against reference COTS optics with a nominally better performance than the payload to ensure that the test scheme is sensitive enough to measure the relevant metric (resolution, MTF) with sufficient accuracy to characterize the payload.Figure 4: a) Example test setup to measure the resolution of a satellite imaging payload as described in Tumarina et al.[16] and b) Mechanical test as proposed by Jeong et al.[20] where a static load emulates mechanical shocks on a payload.WP5: In this work package, the optical and mechanical teams will collaborate to assemble a first lab prototype of the payload. Here, the optical setup built in WP4 can be used to align the optics mounted in the mechanical structure to reach the highest possible performance. These measurements can then be compared to the simulated performance and tolerances, to ensure that specifications are met. If performance is not met, this is likely due to the mounting system, as the optics will all have been individually tested, such that performance deteriorations are due to alignment errors. Using an approach similar to the one described by Blanco [21], the alignment of optical groups in the telescope can be aligned separately to isolate underperforming mounts. The goal here is to verify that the resolution criterion is met to within 10% to account for mechanical tolerances during assembly, integration and testing (AIT). This WP includes 1 month of buffer time to cater for potential redesigns and iterations of the mechanical components.WP6: After successful AIT and demonstration of payload performance under nominal conditions, this work package aims to check for payload performance deterioration when subjected to mechanical stress, in particular to landing shock, under lab conditions. To test this we will use a simple setup to emulate dynamic loads and shocks using static loads as described by Jeong et al. [20] (see Fig. 4b), based on specifications determined in WP1. This test will reveal whether payload positioning is affected by mechanical loads similar to landing shocks, and extends the simulated performance to include the full payload, including bonding joints and similar, which are difficult to simulate. After the loading test, the optical performance is measured again using our test setup. If the measured optical performance degradation is below the tolerances determined as per the optical simulations performed in WP2, we regard this test as passed. If performance deteriorates substantially, this will require mechanical modifications such as increasing stiffness of the optical mounts, which should not require a full redesign of the system due to the modular approach described above. This work package includes 1 month of buffer time to accommodate for potential reworking of the mounts.WP7: To emulate environmental conditions and test optical performance of space payloads, a thermal and vacuum chamber (TVAC) is typically used [17], [22], which emulates the low pressure and temperatures these payloads are exposed to. The stratospheric environment our payloads are exposed to is less severe but harsh nonetheless [3], [15], [17], with external temperatures down to -60ºC and pressures down to 40 mbar, such that TVACs are an attractive test option for this type of payload. However, for the present project, the acquisition cost of such a chamber exceeds the budget. Alternatively, one can perform TVAC testing at dedicated facilities, with the associated costs and delay, which also entails moving and setting up our optical test setup to the location of the TVAC chamber. For the particular case of our flight vehicle technology, a third option exists, which is to directly test fly the payload to verify performance in flight, which is not a feasible option for typical space imaging systems. We favor this approach as it takes advantage of the inherent quick turnover time of our stratospheric platform, which translates to a quick test implementation.