Optical System Design for CubeSats - PowerPoint Presentation

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Optical System Design for CubeSats

Joseph M. Howard, Garrett J. WestOptics Branch, Code 551, GSFC NASA

Agenda

Optical Design Lab (ODL)Optical Specifications

Refractive vs. Reflective

Freeform Optics

Examples

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Welcome to the ODL!!

Optical Design Lab (ODL): Goddard Optics Branch, Bldg

5, Room W054

We provide optical design services, and a gateway to the Engineering Technology Directorate (ETD)

Contact: Joe.Howard@nasa.govThe conversation starts with specifications

…

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Optical Design Specification

What is the NAME

of your mission, the basic concept (one or two sentences), and the top level science requirements ? Are there "competition sensitive" aspects of this study that you need us to be aware?

Are there

s

chedule

constraints ? (e.g. Instrument Design Lab, IDL, or Mission Planning Lab, MPL, run in a few weeks, etc.)

Number

of instruments ? (typically this is just one)

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Optical Design Specification

Conjugates

? Is your object of interest at infinity, which is to be imaged onto a detector? (This case is the most common.)

Aperture

? Is this defined as an Entrance pupil diameter (EPD) ? Or a working F/# ? Is this requirement driven by radiometry (i.e. sensitivity), or resolution (i.e. diffraction limited) ?

Field of view

(FOV)

?

Do you have a detector concept in mind? If so, tell us the pixel size and array size.

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Optical Design Specification

Focal Length or Magnification

? What is your desired Pixel sampling on the object of interest (e.g. sky or ground) ?

O

ptical performance figure of merit ?

Wavelength range

? (i.e. optical

bandpass

)

 If the instrument is a spectrometer, please include desired spectral resolution.

Systems requirements

?

Strongest engineering driver: cost, volume, mass, or performance?

Any optically important mechanisms (e.g. scan or steering mirrors)?

Any significant packaging or mass constraints for this instrument?

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Design Solutions: Refractive

Plot

Aperture (F

/

#) vs FOVRefractive can be more compact

Large

bandpass

may require many lenses for chromatic correction

Mass adds up for complex systems

Glass may be sensitive to radiation environment

Larger field of view capabilityThroughput may be impacted depending on glass transmittance and number of surfaces

LENSES

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Design Solutions: Reflective

Large

bandpass

are easy to accommodate

Larger Fields are challenging to packageUsually higher throughput compared to glassFreeform shapes can help with packaging and performance…

MIRRORS

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Freeform Optics

Definition

: a mirror or a lens with a non-rotationally symmetric surface, typically with large departures from a best-fit spherical surface (many um to mm).

Enables

:

Wider FOV

Better

Image Quality

Smaller

Reduce number of components

Conic Relay

Freeform

Relay

3 mirror

Asphere

Telescope

Traditional Optics

FREEFORM

S

maller

Less mirrors

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2-mirror Freeform

Example System: Focal

2-mirror telescope, 1UField correction lens

UV capable

40 mm Pupil

3D printedE.g. NEAS

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Example System: Afocal

2-mirror afocal

telescope

Pupil imaging concept

UnobstructedInternal Field StopSquare pupilE.g.

BIRCHES,

etc.

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Example: Simple Spectrometer

Refractive objective

Internal Field Stop

Refractive Collimator

Linear GratingRefractive CameraE.g. SHILO

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Example: Wide-Field

Imager

Refractive, 3 U design

80 mm pupil

10 deg fieldCan cover

UV

E.g., CUTIE, GUCI, etc.

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Example: Freeform

2 U 2-mirror focal system

50 mm pupil, deployed

Large Field (3 x 9

deg)F/5Can be folded

Efficient with

space

E.g. XY

Penta

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Example: Freeform

1 U 2-mirror focal system

20 mm pupil, two channel

Large Field (~4x8 degrees)

F/3.2Efficient with spaceE.g. PROVE

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Concluding Remarks

The minimum aperture size of optical instrumentation is often driven by the laws of physics, so miniaturization of optics is often not an option for science applications.

Freeform optics are enabling smaller optical systems of a given aperture with large fields of view

.

If you need help with your optical design, contact the Optical Design Lab (ODL): Joe.Howard@nasa.gov

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