[Webinar] From Concept to CubeSat [Q&A]

Q: You mentioned that the telescope was simulated on-earth but will be utilized in low earth orbit. Are the effects of the vacuum of space considered when looking at performance in OpticStudio?

A: Yes, the vacuum of space can also be considered in an analysis like this. We did go through the process of analyzing the structural deformation effects that result from simulating the pressure environment of space. However, it was found that in comparison to the structural deformation experienced by the optics from the temperature change, the deformation that occurred from just changing the pressure was 2 orders of magnitude lower. Thus, pressure effects did not severely degrade optical performance. For a full analysis of a real space-based system, you will want to include pressure effects even if it has a small effect on performance, just for the sake of having a full engineering model. Simulating temperature and pressure effects also allows for a more accurate comparison when analyzing test results of a system soaked in a thermal vacuum chamber.

Q: Can the Prepare for OpticsBuilder tool in OpticStudio also be used in Sequential mode?

A: Yes, if the optical system in OpticStudio is still in sequential mode when running the Prepare for OpticsBuilder tool, OpticStudio will automatically convert the sequential file to a non-sequential one. This includes: converting the sequential surfaces to matching non-sequential geometry, check to make sure rays are positioned and angled correctly, confirm that spot size change has remained below an allowable value and allow the user to open and inspect the non-sequential. 

@Harvey.Spencer 

Q1: What is the FOV?

A1: The FOV of this example system is ~0.38 degrees. Per the paper that was used as a reference for the optical design, this design can theoretically “take images of a ~4km x ~2.3km area of the Earth’s surface at 700km altitude”. 

Q2: Since the mirrors in this design are aluminum wouldn't you want the housing to be the same aluminum so that the figure changes of the mirrors over temperature will be matched by the proper change in the airspace between the two mirrors?  If the housing has essentially zero expansion, I would think that the system would go out of focus over temperature.  Maybe it has something to do with the spring-loaded mounting bolts?

A2: This is a very interesting suggestion and our material choice was not impacted by the spring loaded mounting. There are designs where you would build the entire instrument from the same material, even machine it from one huge block. We have gone with a different material choice here to show the effect with the new capabilities within STAR. Furthermore, if you would look at a case with a temperature gradient across the assembly instead of the uniform temperature, aluminum would cause much larger deformations that don’t cancel out, so using the same material for all parts is not always the best choice.

@Bruce.Cannon 

Q1: How does this CREO Ansys and FEA differ from the earlier Ansys product Sigfit?

A1: SigFit is not part of the Ansys portfolio, but an independent software product from Sigmadyne. The STAR Module is built directly into OpticStudio which enables you to use a majority of the OpticStudio tools and analyses and see the impact of the FEA data inside of the OpticStudio immediately after loading the FEA data. In addition, the STAR Module features visualizations and a UI that is easy to use and fit into a variety of workflows.
The CREO CAD package was used to create the mechanical geometry with the help of OpticsBuilder. Ansys Mechanical was used to perform the thermal structural FEA simulation.

Q2: Does this come in as different configurations, so like ambient vs colder?

A2: Currently STAR does not support the use of multiple configurations. Instead, each of the datasets is imported to a different OpticStudio file. You can swap the FEA data in one file, but you would have to do a fit each time you changed the FEA data file for a surface. A surface cannot be assigned more than one FEA dataset at a time.
If you are interested in the difference for STAR effects applied, there are several ways to disable the FEA data momentarily or evaluate the difference in a wavefront plot.

@Lisa.gambcorti 

Q1: Can you control the sampling of the surfaces in case of shorter wavelengths?

A1: The fit generated by STAR creates a continuous surface deformation from the discretized FEA result, so there is no actual sampling that you need to worry about in case of shorter wavelengths. However, if you want to capture deformation effects on a very small scale you might need to increase the number of nodes of the FEA mesh. The fit could also be adjusted to capture the FEA node deformation more tightly by increasing the Max Level or the Grid parameters in the STAR Fit Assessment tool.

Q2: Have you validated with environmental test your model results?

A2: The CubeSat example was not validated with any hardware tests as the intent was to demonstrate the workflow with Ansys Zemax software. The STAR module itself has been used and tested by several costumers where the results matched their measurements. In addition, we've compared to the OpticStudio "Make Thermal" tool, to Grid GRINs (using .GGD files), as well as other known results - like deformations with a known shape, where we can verify that the fit is returning the expected shape.