Project Description

Highly Collimated Solar Simulator with automated beam angle movement

The solar simulator was developed for a prominent national space agency. The agency has a range of projects requiring solar simulation and when a new project appeared with stringent requirements, they approached Sciencetech to provide a highly accurate solar simulation system.

Sciencetech High Collimated

Customer Requirements

The solar simulator was developed for a prominent national space agency. The agency has a range of projects requiring solar simulation and when a new project appeared with stringent requirements, they approached Sciencetech to provide a highly accurate solar simulation system.

Some members of the customer agency had hands-on experience using one of Sciencetech’s highly collimated solar simulators several years ago. For a new project testing their satellite sensors prior to launch, they required a larger, more sophisticated version of this solar simulator. They reached out to Sciencetech and asked if we could provide a solar simulator with an extraordinarily close match to the Sun in terms of irradiance, collimation angle, and spectral match.

Additionally, they wanted automation to manipulate the solar simulator in X, Y, Z, and 2 rotation angles. Initial discussions considered several automation implementations and initial engineering analysis determined that the physical limitations of xenon short arc lamps would make it very challenging to meet the desired specifications for collimation along with the other criteria. Sciencetech determined a method to achieve the most important specifications and presented it to the customer. The guidelines and criteria were approved and Sciencetech initiated the designing of the project.

Requirement

The customer had precise guidelines for:

Collimation Full Angle: 90% power within 0.69°
Target Size: 33 cm diameter
Spatial Non-uniformity:  2.95% (Class A)
Temporal Instability:  1.5% (Class A)
Intensity  1366 W/m2 (AM0 spectral match)
Attenuated Intensity:   1.366W/m2 (down to 0.1% attenuation)
Output Direction:  Horizontal

Ideation and designing the system

Optical ray tracing path of the light source 

During the design process, we used a combination of optical modeling and mathematical analysis to solve the multi-faceted challenge of how to make a highly uniform and intense light source with a large target area, specific spectral match and divergence angle approaching that of the sun.

The optical design structure

An ellipsoidal back reflector collected a significant portion of the lamp emission and focuses into a homogenizing light pipe. This light pipe guides the light via total internal reflection and the many reflections serve to mix the light rays, making the output more uniform. An array of lenses and turning mirrors were used to direct the light to a collimating mirror which reflects the light to form nearly parallel rays, producing high irradiance and low beam divergence at the target plane.

Output spectrum of the solar simulator in relation to AM0 spectrum 

Irradiance distribution on the target area as simulated by the optical simulation software

Mechanical Design for Automated Motion Control

Our customer required automated motion of the entire solar simulator in 5 axes—X, Y, and Z, as well as 2 axes of rotation. Additionally, the entire system needed to operate inside a cleanroom, necessitating isolation of the solar simulator’s air cooling system.

Sciencetech designed an automated mechanical stage and custom software to meet these automation goals, and provided a special cooling design, instrument components, and housing design to meet these needs.

The motorized movement system was built and tested and its software was created in-house. The movement system, housing, software, and optical elements were completed according to the customer’s specifications for all 5 axes of movement and a software GUI was included for easy control.

Custom Solar Simulator

Moving system of the solar simulator to provide automated motion of the entire solar simulator in 5 axes as envisioned by our mechanical engineers

A drawing of the solar simulator system comprising of ISO7 compatible clean room housing with a depiction of the highly collimated rays emerging from the output of the system 

Prototype Design and development

A high powered 6.5 kW Xenon arc lamp was used as the base light source to simulate the solar radiation. The xenon lamp spectrum was modified using an air mass filter to meet AM0 spectral matching criteria.

The irradiance was achieved down to 0.1% of its full power with near continuous attenuation maintaining the spatial uniformity, spectral match and temporal stability.

spatial non-uniformity map

The temporal stability was measured over short, medium and long-term periods and met Class A specifications.

We achieved a high degree of collimation with 90% power within 0.69° full angle. The high collimation provided an equally uniform spot at several distances from the solar simulator output.

Temporal stability of the irradiance measured over 30 minutes

Radiance measurement of the solar simulator output with respect to collimation angle.

Clean Room Requirements

The entire system was sealed for use in a clean room, including an isolated air cooling system preventing contamination of the clean room environment. The entire system was compliant with ISO Class 5 clean room standards.

Acceptance Testing and Installation

Frequent contact with the customer’s team allowed Sciencetech’s engineers to make modifications to the design to ensure a better transition to the customer, and to help the customer gain confidence in the capabilities of the device they ordered. The final acceptance test was created in conjunction with the customer’s engineers, ensuring the instrument would operate within the parameters they needed the moment the device left Sciencetech. The final integration of hardware and software was completed at the end-user’s facilities, and the device passed acceptance testing with full approval.

Automated moving system of the solar simulator being tested at Sciencetech’s facility

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