PHYS 490 - wiki.heprc.uvic.ca

PHYS 490 ORCASat and ALTAIR Development

Report 3

Josh Gage, V00876655

April 24th, 2020

Instructor: Dr. Justin Albert

PHYS 490 ORCASat and ALTAIR Development 1

University of Victoria Department of Physics

Table of Contents Table of Figures ............................................................................................................................................ 2

Executive Summary ...................................................................................................................................... 4

Background ................................................................................................................................................... 5

Introduction ................................................................................................................................................... 6

Design Progress ............................................................................................................................................ 6

Optical Payload Mechanical Design ......................................................................................................... 9

Integrating Sphere ................................................................................................................................... 10

Previous Integrating Sphere Designs .................................................................................................. 10

Updated Design ................................................................................................................................... 11

Laser Diode Heatsink .............................................................................................................................. 13

Previous Laser Diode Heatsink Designs ............................................................................................. 13

Present Design .................................................................................................................................... 13

Testing ........................................................................................................................................................ 17

Basic Electronics Functionality .............................................................................................................. 20

Introduction ......................................................................................................................................... 20

Results ................................................................................................................................................. 20

Discussion ........................................................................................................................................... 21

Unobstructed Laser Light and Effect of Optical Stops ........................................................................... 21

Results ................................................................................................................................................. 21

Discussion ........................................................................................................................................... 23

Next Steps ................................................................................................................................................... 26

Conclusion .................................................................................................................................................. 26

References ................................................................................................................................................... 27

Appendices .................................................................................................................................................. 28

Appendix A: Spring 2018 Optical Payload Design (HOMATHKO) ..................................................... 28

Appendix B: Summer 2019 Optical Payload Design (ORCASat) .......................................................... 29

Appendix C: Winter 2020 Optical Payload Design (ORCASat) ............................................................ 30

Appendix D: Electrical Circuit Schematics ............................................................................................ 31

Appendix E: Test Plan Objectives .......................................................................................................... 33

Laser Diode Module Test Plan................................................................................................................ 33

1. Basic Electronics Functionality .................................................................................................. 33

2. Basic Optical Properties of Laser Diodes ................................................................................... 33



3. Optical Noise Measurement ........................................................................................................ 33

4. Thermistor Calibration ................................................................................................................ 33

5. Active Power Control Accuracy ................................................................................................. 33

6. Temperature Gradient Between Laser Diode Case and Heatsink ............................................... 34

7. Wavelength Drift per Temperature Variation ............................................................................. 34

8. Failure of Laser Diode Driver ..................................................................................................... 34

9. Laser Diode Temperature-testing in Vacuum ............................................................................. 34

Appendix F: Unobstructed Laser Light and Effect of Optical Stops Photos .......................................... 35

Table of Figures Figure 1: ORCASat concept design .............................................................................................................. 5

Figure 2: Optical payload mechanical assembly, isometric view ................................................................. 7

Figure 3: Optical payload mechanical assembly, parts list ........................................................................... 7

Figure 4: Optical payload mechanical assembly, front view ....................................................................... 7

Figure 5: Optical payload mechanical assembly, front bolt section view and front laser diode section

view ............................................................................................................................................................... 8

Figure 6: Optical payload mechanical assembly, right view ........................................................................ 8

Figure 7: Optical Payload mechanical assembly, top view ........................................................................... 8

Figure 8: A fiber-optic laser guide ................................................................................................................ 9

Figure 9: ORCASat’s first Payload Design featuring two angled laser diode access ports ......................... 9

Figure 10: Vertical optical payload mechanical assembly, right laser diode section view ......................... 10

Figure 11: Integrating sphere upper hemisphere, isometric view ............................................................... 12

Figure 12: Integrating sphere upper hemisphere, front view ...................................................................... 12

Figure 13: Integrating sphere upper hemisphere, right view ...................................................................... 12

Figure 14: Laser diode module, isometric .................................................................................................. 14

Figure 15: Laser diode module, top view ................................................................................................... 14

Figure 16: Laser diode module, left view ................................................................................................... 14

Figure 17: Laser diode module, left laser diode section view ..................................................................... 15

Figure 18: Laser diode PCB, top-view (designed by Trevor Zakus for ECE 490) ..................................... 15

Figure 19: Laser diode PCB, bottom view (designed by Trevor Zakus for ECE 490) ............................... 16

Figure 20: 3M 203-6970-50-0602J laser diode socket ............................................................................... 16

Figure 21: Payload PC104 motherboard design, top view (designed by Evan Moore for ECE 490) ......... 17

Figure 22: Payload PC104 motherboard design, front view (designed by Evan Moore for ECE 490) ...... 17

Figure 23: Test Setup, Diagram .................................................................................................................. 18

Figure 24: Home Test Setup, Top View ..................................................................................................... 19

Figure 25: Home Test Setup, Front View ................................................................................................... 19

Figure 26: Home Test Set-up, Back View .................................................................................................. 20

Figure 27: Home Test Setup, Diode View .................................................................................................. 20

Figure 28: Laser light spread (28 [in] diameter) at 44.5 [in] with no optical stop ...................................... 21

Figure 29: Laser light spread (10 [in] diameter) at 44.5 [in] with 11/64 [in] optical stop at 0.375 [in] ..... 22



Figure 30: Laser light spread (4.5 [in] diameter) at 44.5 [in] with 3/32 [in] optical stop at 0.375 [in] ...... 22

Figure 31: Laser light spread (2.5 [in] diameter) at 44.5 [in] with 1/16 [in] optical stop at 0.75 [in] ........ 23

Figure 32: Examination of incident light features....................................................................................... 24

Figure 33: Plot of laser diode spread angle vs optical stop diameter .......................................................... 25

Figure 34: Plot of spread angle of maximum wing length vs optical stop diameter ................................... 26

Figure 35: Homathko’s Optical Payload Design, isometric view ............................................................... 28

Figure 36: Homathko’s Optical Payload Design, front view ...................................................................... 28

Figure 37: Homathko’s Optical Payload Design, right view ...................................................................... 28

Figure 38: ORCASat’s First Optical Payload Design, isometric view ....................................................... 29

Figure 39: ORCASat’s First Optical Payload Design, front view .............................................................. 29

Figure 40: ORCASat’s First Optical Payload Design, right view .............................................................. 29

Figure 41: ORCASat’s Second Optical Payload Design, isometric view ................................................... 30

Figure 42: ORCASat’s Second Optical Payload Design, front view .......................................................... 30

Figure 43: ORCASat’s Second Optical Payload Design, right view .......................................................... 30

Figure 44: Laser diode heatsink circuit board schematic (designed by Trevor Zakus for ECE 490) ......... 31

Figure 45: Laser diode driver circuit board schematic (designed by Evan Moore for ECE 490) ............... 31

Figure 46: Temperature-monitoring circuit schematic (designed by Evan Moore for ECE 490) ............... 32

Figure 47: Payload motherboard circuit schematic (designed by Evan Moore for ECE 490) .................... 32

Figure 48: Incident laser light with no optical stop, featuring a 28” main diameter and an 18” wing, 44.5”

away. ........................................................................................................................................................... 35

Figure 49: Incident laser light with a 13/64" optical stop at 0.375", featuring a 12.5" main diameter and a

10" wing 44.5" away. .................................................................................................................................. 35

Figure 50: Incident laser light with a 3/16" optical stop at 0.375", featuring a 11" main diameter and a 9"

wing 44.5" away. ......................................................................................................................................... 35

Figure 51: Incident laser light with a 11/64" optical stop at 0.375", featuring a 10" main diameter and a

8" wing 44.5" away. .................................................................................................................................... 36


wing 44.5" away. ......................................................................................................................................... 36

Figure 53: Incident laser light with a 9/64" optical stop at 0.375", featuring a 8.5" main diameter and a 8"

wing 44.5" away. ......................................................................................................................................... 37

Figure 54:Incident laser light with a 1/8" optical stop at 0.375", featuring a 7" main diameter and a 6.5"

wing 44.5" away. ......................................................................................................................................... 37


wing 44.5" away. ......................................................................................................................................... 37


wing 44.5" away. ......................................................................................................................................... 38


wing 44.5" away. ......................................................................................................................................... 38

Figure 58: Incident laser light with a 1/16" optical stop at 0.750", featuring a 2.5" main diameter no wing

44.5" away. ................................................................................................................................................. 38



Executive Summary This report contains an overview of work completed on the ORCASat Optical Payload project during the

spring 2020 semester.

During the January 6th to March 31st period, work included: personnel onboarding and literature review,

mechanical designs and drawings of the vertical and horizontal integrating spheres and laser diode

heatsinks, and electrical design of laser diode boards and laser diode driver boards (completed by Evan

Moore and Trevor Zakus for ECE 490). The vertical configuration is preferred, and was designed around

placing the 660 nm and 840 nm (or 405 nm or 980 nm) laser diodes as near to colinear as possible to

minimize the difference between intensities measured by the two onboard photodiodes.

During the March 31st to April 24th period (since report 2), further work included: the testing of the basic

electronics functionality of the MLD203P2E laser diode driver and the L660P120 laser diode using a

Thorlabs MLDEVAL board, the testing of basic optical properties of laser diodes in a dark room, and the

design of the transimpedance amplifier (completed by Evan Moore and Trevor Zakus for ECE 490).

The first test verified that the L660P laser diode, the MLD203P2E driver, and the MLDEVAL board all

function as expected. The second test revealed that the L660P120 laser diode produces a roughly-circular

spread of speckled incident light on a flat, perpendicular surface with a maximum main-diameter spread

angle of 18 degrees and a single wing with a maximum spread angle of 45 degrees. This test also revealed

that optical stops can greatly reduce the spread angles of the incident light’s main-diameter and can also

greatly reduced the spread angles of its wing. Therefore, optical stops should be further investigated for

implementation in the laser diode heatsink design.

Next steps will include testing the power output of the 660 nm laser diode with a Thorlabs optical power

meter, designing a test jig for further optical stops testing for the L660P laser diode, inquiring with

Thorlabs about a modified laser diode driver that can provide 5V to operate the 405 nm laser diode,

testing various combinations of laser diodes and photodiodes, thermal simulation of laser diodes and laser

diode heatsinks, and optical simulation of laser diode beams inside the integrating sphere.



Background ORCASat’s Optical Payload will serve to photometrically calibrate astronomical reference objects (stars

known as standard candles) which ground-based telescopes use in turn for daily calibration. Note that

ORCAsat’s Optical Payload will also be capable of directly calibrating ground-based telescopes. To

photometrically calibrate astronomical reference objects, it must operate two monochromatic light sources

in low earth orbit with power simultaneously measured onboard the satellite and on the ground by

telescopes. Comparing these measured target intensities will reduce the photometric uncertainty of

ground-based telescopes by at least an order of magnitude.

Figure 1: ORCASat concept design

Thus, the Optical Payload has three main functions:

1. Generate target light of two constant wavelengths and constant powers in low earth orbit that can

be observed by ground-based telescopes during an observation period.

2. Measure the optical power of the generated light onboard the spacecraft.

3. Downlink measured optical power values for the duration of the observation period.

The scope of this report includes initial design and development of functions 1 and 2.

Further design requirements are set by the Canadian Space Agency and by Nanoracks, who are hosting

the cubesat deployer on the International Space Station from which ORCASat will be launched in 2021.

The Canadian Space Agency requires that ORCASat complies with:

• NASA’s off-gassing requirement (that all parts off-gas less than 0.1% of mass)

• NASA’s guideline for hazardous materials (that no parts are made from hazardous materials)

Nanoracks requires that ORCASat adheres to:

• PC104 embedded computer standards

• A 2U total satellite geometry (10cm x 10cm x 20cm)

• Nanoracks’ vibration testing standards



Introduction To generate target light of two constant wavelengths and constant powers that can be observed by ground-

based telescopes during an observation period, two laser diodes will be employed: one with a 660 nm

wavelength, and another of on of 405 nm, 840 nm, or 980 nm wavelength. To measure the optical power

of generated light onboard the spacecraft, two photodiodes will be employed. Both laser diodes and both

photodiodes will be mounted to an integrating sphere, which diffusively reflects the directional laser

source light, allowing for the light to be measured by an observer and by the onboard photodiodes during

the same observation period. The integrating sphere also ensures that the light emitted from the spacecraft

is uniform, and that the photometric reference calibration quality is not dependent on viewing angle.

Table 1: ORCASat Optical Payload Design Requirements

During the January 6th to April 24th period, mechanical design work (Josh Gage) included:

• Design of horizontal integrating sphere (featuring a horizontal laser diode configuration)

• Design of horizontal laser diode heatsink (featuring a horizontal laser diode configuration)

• Design of vertical integrating sphere (featuring a vertical laser diode configuration)

• Design of vertical laser diode heatsink (featuring a vertical laser diode configuration)

• Production of vertical integrating sphere drawing package (see attached)

• Production of vertical laser diode heatsink drawing package (see attached)

• 3D-Printing a prototype of the vertical integrating sphere

• 3D-Printing a prototype of the vertical laser diode heatsink

• Testing basic electronics properties of the L660P120 laser diode and MLD203P2E driver

• Testing basic optical properties of the L660P120 laser diode and the effect of optical stops

Also, during the January6th-April 24th period, Electrical design work (Evan Moore and Trevor Zakus)

relevant to this report included:

• Design of the laser diode boards

• Production of laser diode board drawings

• Design of the laser diode driver board (Optical Payload PC104 motherboard)

• Production of laser diode driver board drawings

• Ongoing design of the transimpedance amplifier board

Design Progress Design progress included redesigning the Homathko integrating sphere and designing laser diode

modules in both vertical and horizontal laser diode configurations. The vertical configuration is preferred,

and will be the main subject of this report—although the horizontal configuration may be later

implemented according to future test results or future design considerations.

Design Requirement Solution

Generate monochromatic 660 nm light source Thorlabs L660P120 - 660 nm, 120 mW, Ø5.6 mm, C Pin Code, Laser Diode

Generate second monochromatic light source Thorlabs L840P200 - 840 nm, 200 mW, Ø5.6 mm, C Pin Code, Laser Diode

OR Thorlabs

OR U.S. Lasers D405-120, 120mW, Ø5.6 mm, B Pin Code, Laser Diode

Optimize light source viewing angle and uniform power distribution per area 2" ID Integrating Sphere

Measure optical power onboard spacecraft Two Photodiodes



Figure 2: Optical payload mechanical assembly, isometric view

Figure 3: Optical payload mechanical assembly, parts list

Figure 4: Optical payload mechanical assembly, front view



Figure 5: Optical payload mechanical assembly, front bolt section view and front laser diode section view

Figure 6: Optical payload mechanical assembly, right view

Figure 7: Optical Payload mechanical assembly, top view



Optical Payload Mechanical Design The initial vertical integrating sphere and vertical laser diode heatsink design configuration was

completed.

This configuration was designed around the need to have laser diodes’ laser beams as near to colinear as

possible. This is desired as it allows the two photodiodes to read as near to same power from each of the

laser diodes as possible, as the laser beams from the 660nm and the second laser diode will strike the

inside of the integrating sphere at two points that are close with respect to the photodiodes before diffuse-

reflecting. To get the laser beams as close as possible, there are three options:

1) Implement a laser guide for the two beams at a single access port:

This solution was deemed to be overly complex for use onboard the satellite by previously

involved members.

Figure 8: A fiber-optic laser guide

2) Mount the two laser diodes onto two angled access ports such that their laser beams would be

incident on the same point inside the integrating sphere:

This solution was deemed to be unsatisfactory by Prof. Justin Albert because laser beams should

be incident on the interior of the integrating sphere with the same incident angle.

Angled beams should be avoided as the imperfections in the integrating sphere will not perfectly

diffuse-reflect the laser light. If the light is not perfectly diffuse-reflected, the difference in

incident angles will cause exposure differences between the two photodiodes. By ensuring the

angle of incidence is the same, it can be ensured that both photodiodes will be exposed to an

equivalent amount of light. This can be achieved by designing the laser diodes such that their

emissions are as co-linear as possible.

Figure 9: ORCASat’s first Payload Design featuring two angled laser diode access ports

3) Mount the two laser diodes onto a single access port such that they are parallel with minimum

distance between them:



This solution was deemed to be most satisfactory by Prof. Justin Albert so long as the laser diodes

have an absolute minimum distance between them. This is to ensure that light from the two lasers

strikes the opposite side of the integrating sphere interior surface in as similar a way as possible.

This was achieved by mounting the two laser diodes such that their mounting cases are parallel

and nearly in contact, with a total center-to-center distance of 6.5mm (laser diode mounting cases

are 6mm in diameter).

Figure 10: Vertical optical payload mechanical assembly, right laser diode section view

Integrating Sphere The vertical integrating sphere design was completed.

The integrating sphere serves to diffusively reflect two directional laser source lights, allowing for the

light to be measured by an observer and by the onboard photodiodes during the same observation period.

Furthermore, it ensures that the light emitted from the spacecraft is uniform, and that the photometric

reference calibration quality is not dependent on viewing angle.

Previous Integrating Sphere Designs

This design is a revision of the design concept established by the ALTAIR balloon payload, and

integrating sphere designs from Spring 2018, Summer 2019, Winter 2020 (see Appendix A, B, C):

• The Spring 2018 integrating sphere design failed to meet current requirements as it only

accommodated a single laser diode and did not have a simple assembly procedure (see Appendix

A).

• The Summer 2019 integrating sphere design failed to meet current requirements as the laser

emissions were not optimized to be as colinear as possible and it was also not optimized for

fabrication and assembly, resulting in high cost estimates and complicated assembly procedures

(see Appendix B).

• The Winter 2020 integrating sphere design failed to meet current requirements as it featured two

laser diode access ports mounted 90 ° from the photodiode modules.

In this case, it suffered the same design drawbacks as the first ORCASat integrating sphere did

due to angled laser diode access ports—however, these drawbacks were further aggravated by

increasing the separation between laser diode access ports, having the laser diode access ports



angled such that laser diode beams were incident at different points on the southern hemisphere

(see Appendix C).

Updated Design

The vertical design was based directly off of the first ORCASat Optical Payload design (see appendix C).

The sphere’s interior dimensions were not changed, as they could remain the same while meeting other

design requirements. Interior diffuse-reflective coating is to remain Avian-B. Avian-B meets diffuse-

reflectivity requirements and is readily available from Dr. Justin Albert.

Changes to the integrating sphere include:

1. A single, slotted laser diode access port replaced the two laser diode access ports to meet the

requirement of nearly-colinear laser diode laser beams.

2. The integrating sphere’s north hemisphere wall was thickened to feature larger flat faces for the

laser diode access port and the two photodiode access ports to meet the requirement for locating

features on each access port. Consequently, the integrating sphere’s mounting holes were located

on a new (30mm) diameter. This increases the payload’s mass slightly, but ORCASat remains

under overall mass requirements. Exact increase and margins to be included in future

documentation.

3. Laser diode module and photodiode module access ports were altered. This included:

o Removing excess material from laser diode access ports. This allowed the laser diode

heatsink to be mounted directly onto a flat face milled into the integrating sphere’s

surface with an adhesive (as was already done for the photodiode modules). This was

done to improve the feasibility of integrating sphere fabrication

o Locating holes and edges were added to the laser diode module access port for ease of

assembly and increased quality of adhesion. This will allow for accurate mounting and

adhesion of the laser diode module with respect to access ports’ planar direction and

orientation (in this case oriented as the vertical laser diode configuration).

o Locating holes were added to photodiode module access ports for ease of assembly and

increased quality of adhesion. This will allow for accurate mounting and adhesion of

photodiode modules with respect to access ports’ location (no planar directional

preference for photodiodes).

Table 2: Integrating sphere design requirements


Provide diffuse-reflective surface inside integrating sphere Avian-B coating

Prevent laser diodes from directing light directly into photodiodes Laser diodes and photodiodes all mounted in earth-facing hemisphere of integrating sphere

Investigate wings and speckle of laser diodes

Implement necessary optical stop



Figure 11: Integrating sphere upper hemisphere, isometric view

Figure 12: Integrating sphere upper hemisphere, front view

Figure 13: Integrating sphere upper hemisphere, right view



Laser Diode Heatsink The initial vertical laser diode heatsink design configuration was completed. This design is significantly

different from all of this project’s previous laser diode heatsink designs, as it needed to address the new

requirements of housing two laser diodes in a single heatsink to mount to a single access port on the

integrating sphere, and of including on-board temperature monitoring of laser diodes during operation.

Previous Laser Diode Heatsink Designs

This design is an alternative to Homathko and ORCASat laser diode housing designs (see Appendix A, B,

C):

• The Spring 2018 laser diode insertion point failed to meet present requirements as it only

accomadated a single laser diode, did not include on-board temperature monitoring during

operation.

• The Summer 2019 laser diode heatsink failed to meet requirements as it only accommodates a

single laser diode, and did not include on-board temperature monitoring during operation.

• The Winter 2019 laser diode heatsink failed to meet present requirements as it only

accommodates a single laser diode.

Present Design

The vertical laser diode heatsink is designed to mount two parallel laser diodes to a single access port on

the integrating sphere such that the laser diodes are as near colinear as possible.

The aluminum body acts as a heat sink for the laser diodes, while the laser diodes’ temperatures are

monitored by two thermistors that accesses the base of the laser diode through the side of the heat sink.

6061-T6 Aluminum was selected for the laser diodes’ heatsink body because it is a good conductor, meets

NASA off gassing and hazardous materials requirements, is readily available, is easy to manufacture, and

has low cost. The laser diodes’ temperatures are monitored by two thermistors that are potted in the

heatsink to access the base of the laser diodes. Temperature measurement is performed at the base of the

laser diodes, as their bases are the source of heat during operation. To minimize thermal resistance

between the diodes and the thermistors, thermistors will be potted with minimal heatsink material

between them and the laser diodes’ bases. The selected thermometer is a thermistor with an analog-to

digital conversion circuit (see Appendix D). The decision to use a thermistor instead of a digital

temperature sensor or a thermocouple is outside of the scope of the scope of this report but will be

included in future documentation.

The module also features two M3x0.5 threaded holes, which will be used to mount the laser diode boards

to the heatsink, and also during testing to mount the laser diode module as needed.

The laser diode module’s aluminum heatsink body also features a locating edges and extrusion for ease of

assembly and quality of adhesion when mounted to the integrating sphere.

Table 3: Laser diode heatsink design requirements


Mount laser diodes Thorlabs S7060R - Laser Diode Socket for Ø5.6 mm Laser, 3 Pin

Drive laser diodes Thorlabs MLD203P2 - Constant Power LD Driver, SMT Package, for Pin Codes C and D

Monitor laser diode temperatures TDK Electronics B57861S0103F040 THERMISTOR NTC 10KOHM 3988K BEAD

Regulate laser diode temperatures Lase diode module heat sinks



Figure 14: Laser diode module, isometric

Figure 15: Laser diode module, top view

Figure 16: Laser diode module, left view



Figure 17: Laser diode module, left laser diode section view

To minimize noise, laser drive circuitry would ideally be located in the laser module. It was moved off

due to size constraints, leaving a small laser module PCB mounted to the top of the laser diode heat sink

modules (not shown in figures, see appendix A for laser diode circuit board schematic and pcb) that will

feature two thermistors and a 660 nm laser diode and one of a 405 nm, a 840 nm, or 980 nm laser diode.

Figure 18: Laser diode PCB, top-view (designed by Trevor Zakus for ECE 490)

Instead of soldering the thermistors (that has their own wiring off-the shelf) directly to the heatsink board,

a two-pin connector will connect the thermistor to the board so that it can be swapped out or changed

during the design process. Off-the-shelf 3M 203-6970-50-0602J laser diode sockets will connect the laser

diode to the heatsink board. Although the LP660 and LP840 laser diodes are shown in figures, the LP980

is also compatible as all three laser diodes use the same 5.6 mm diameter TO can case. However, the 405

nm laser diode requires 5V, and the MLD203P1 laser diode driver (for pin code B laser diodes, se figure

21) can only deliver 3V. Thus, a modified laser diode driver board is being investigated from Thorlabs.



Figure 19: Laser diode PCB, bottom view (designed by Trevor Zakus for ECE 490)

Figure 20: 3M 203-6970-50-0602J laser diode socket

The electrical layout of the optical payload will be summarized here, but not discussed (see Appendix D).

Details are outside of the scope of this report.

A five-pin cable will connect the heatsink board to the laser driver board, located on the payload PC104

motherboard located next to the integrating sphere in the payload module. On the five-pin cable, three

pins are for the laser diode and its built-in photodiode (they share a common ground but have separate

anodes), and two pins for the thermistor. This cable was selected to based on the peak current drawn by

the laser diode, and on the assumption that it the cable would not require shielding. If shielding is found

to be necessary during testing, then this cable will be reconsidered. This same five-pin cable is also used

elsewhere on the spacecraft, allowing for shared parts compatibility and expensive crimping tools.



Figure 21: Payload PC104 motherboard design, top view (designed by Evan Moore for ECE 490)

Figure 22: Payload PC104 motherboard design, front view (designed by Evan Moore for ECE 490)

Testing For full test procedures, see the “Laser Wings and Optical Stops Test Plan” document.

Testing progress included basic electronics functionality testing, unobstructed laser light testing, and the

effect of optical stops on laser light testing. Testing was performed on the L660P120 laser diode and the

MLD203P2E driver with a Thorlabs MLDEVAL board. Results of the basic electronics testing included



successful operation of the 660 nm laser diode using the MLD203P2E laser driver and the MLDEVAL

board. Results of the optical stop testing include photographs of incident light on the target wall to

investigate the presence of laser wings and the laser speckle’s uniformity, and a calculation of the laser’s

angle of spread in its main diameter and in its wing.

Due to social-distancing and the COVID-19 pandemic, these tests were performed at a member’s home

using equipment from the ORCASat lab in UVic’s Centre for Aerospace Research. Tests were performed

in a basement room at night with blinds and a blackout curtain on the windows, with no other light

sources present in the room (aside from the single green light on the MLDEVAL board itself—see light

blocker in figure 24). The optical stops were positioned as close to the front of the laser diode heatsink as

possible. Due to the equipment available, this was at 0.375 inches from the front of the laser diode

heatsink (except for the tests of the 5/64 inch and 1/16 inch diameter optical stop holes, which were at

0.500 inches and 0.750 inches respectively due to equipment limitations).

While these tests served as a successful initial examination of basic laser diode electronic and optical

properties, the next round of testing should incorporate a custom 3D-Printed test assembly, to allow for

the optical stop plate to be placed as near to the laser diode heat sink as possible (and at adjustable

distances), while ensuring the alignment and proper relative orientation of the laser diode and the optical

stops.

Figure 23: Test Setup, Diagram



Figure 24: Home Test Setup, Top View

Figure 25: Home Test Setup, Front View



Figure 26: Home Test Set-up, Back View

Figure 27: Home Test Setup, Diode View

Basic Electronics Functionality

Introduction

The basic electronics functionality test was comprised of basic electronics tests of the L660P120 laser

diode and the MLD203P2E driver on the MLDEVAL board, including:

• Verifying that the laser diodes turn on and off

• Verifying that the laser diode driver power control is operational

Results

This test successfully verified that the 660 nm laser diode could be turned on and off and have its input

power controlled by the laser diode driver using the potentiometers on the MLDEVAL board.



Discussion

Once the MLDEVAL board was set up according to its operation manual with the 660 nm laser diode (pin

code C) and the MLD203P2E laser diode driver, the 660 nm laser diode would still not turn on by fine

adjustment of the potentiometer P2 as recommended in the operation manual. Note that the potentiometer

P2 does not have a clockwise or counter clockwise limit position as is suggested in the MLDEVAL

operation manual. Thus, as the laser diode only operates in a small voltage window, the variable

resistance across P2 had to be accurately measured to get within operational voltage range. Once in range,

the laser diode could be turned on and off and have its power adjusted the fine adjustment of the

potentiometer P2 on the MLDEVAL board.

Furthermore, it was realized that the 405 nm laser diode (pin code B) could not run with the MLD203P1E

laser diode driver as the 405nm laser diode requires 5V and the MLD203P1E can provide a maximum of

3V. Thus, a quote is being sought from Thorlabs for an alternative laser diode driver that can run the 405

nm laser diode, and that ideally would have the same form factor and interference requirements as the

MLD203P2E and MLD203P1E laser diode drivers to be compatible with the payload’s electrical design.

This form factor and interference requirement is outside of the scope of this report but will be included in

future documentation.

This test can also be performed for the 840 nm and 980 nm laser diodes once an infra-red camera is

obtained—this will likely be a modified raspberry pi camera.

Unobstructed Laser Light and Effect of Optical Stops The unobstructed laser light and effect of optical stops test was comprised of basic optical tests of the 660

nm laser diode, including:

• Examining the spread of laser light from the L660P120 laser diode

• Examining the presence of laser light “wings” from the incident laser light

• Examining the effect of various sizes of optical stops on laser light spread and laser lights wings

Results

Figure 28: Laser light spread (28 [in] diameter) at 44.5 [in] with no optical stop



Figure 29: Laser light spread (10 [in] diameter) at 44.5 [in] with 11/64 [in] optical stop at 0.375 [in]

Figure 30: Laser light spread (4.5 [in] diameter) at 44.5 [in] with 3/32 [in] optical stop at 0.375 [in]



Figure 31: Laser light spread (2.5 [in] diameter) at 44.5 [in] with 1/16 [in] optical stop at 0.75 [in]

For complete set of test photos, see appendix F.

Table 4: Unobstructed laser light and optical stops testing data

Discussion

Using collected data, angles of spread for the incident laser light and maximum wing were determined—

note that a single wing was visible in all tests aside from the very last test that had no wing (1/16 inch

optical stop at 0.75 inch in front of laser diode heatsink). All tests that used an optical stop also

demonstrated a uniform speckle pattern inside of the incident diameter.

Diameter of optical stop used [in] Incident diameter of light [in] Laser diode heatsink distance to optical stop [in] Maximum Normal Wing Length [in]

0 28 0 18

13/64 12.5 0.375 10

3/16 11 0.375 9

11/64 10 0.375 8

5/32 9 0.375 8

9/64 8.5 0.375 8

1/8 7 0.375 6.5

7/64 6 0.375 5

3/32 4.5 0.375 4

5/64 4 0.5 5

1/16 2.5 0.75

**Distance from laser diode heatsink front to target wall: 44.5 [in]



Figure 32: Examination of incident light features

The spread angle for the incident laser light was calculated as:

𝜃 = arcsin (

𝐷2

44.5 [𝑖𝑛])

With D = Incident diameter of light in inches.

Table 5:Spread angles of incident diameters of light of unobstructed laser light and optical stops



Figure 33: Plot of laser diode spread angle vs optical stop diameter

The spread angle of wings of unobstructed laser light and optical stops was calculated as:

𝛼 = arcsin (

𝐷2 + 𝑊

44.5 [𝑖𝑛])

With D = Incident diameter of light in inches, and W = Maximum normal wing length in inches.

Table 6: Spread angles of wings of unobstructed laser light and optical stops

y = 44.682x - 1.054

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

8.00

9.00

0 1/20 1/10 3/20 1/5 1/4

Lase

r Sp

read

An

gle

[deg

]

Optical Stop Diameter [in]

660 nm Laser Diode Laser Spread Angle vs. Optical Stop Diameter at 44.5 [in] Dist. to Wall



Figure 34: Plot of spread angle of maximum wing length vs optical stop diameter

As shown in the plots above, this test reveals that the spread angle for incident light increases linearly

with the diameter of the optical stop, up to a maximum angle of 18 degrees (with no optical stop), and that

the max wing spread angle also increases linearly with the diameter of the optical stop, up to a maximum

angle of 45 degrees (with no optical stop). This suggests that an optical stop could be of value to the laser

diode heatsink design, and that a second round of testing on the effect of optical stops should be

performed to determine what size of optical stop should be used on the spacecraft, and what the distance

between the optical stop and the laser diode need be.

Therefore this test successfully revealed a roughly circular spread of speckled laser light from the

L660P120 laser diode on a flat, perpendicular target surface; revealed the presence of a single laser light

wing; and demonstrated that optical stops can effectively minimize the spread angle of both the incident

light diameter and the wing from the L660P120 laser diode.

Next Steps Immediate next steps in designing and testing the ORCASat Optical Payload include: testing the power

output of the 660 nm laser diode with a Thorlabs optical power meter, designing a test jig for further

optical stops testing for the L660P laser diode, inquiring with Thorlabs about a modified laser diode

driver that can provide 5V to operate the 405 nm laser diode, testing various combinations of laser diodes

and photodiodes, thermal simulation of laser diodes and laser diode heatsinks, and optical simulation of

laser diode beams inside the integrating sphere.

Conclusion Work completed during the January 6th to April 24th period has included extensive design development

and preliminary testing of the ORCASat optical payload.

Design development was focused on situating the laser diodes parallel and as close together as possible,

such that the light from the two lasers strikes the opposite side of the integrating sphere interior surface in

as similar a way as possible. This will minimize the difference between light intensities measured by the

two onboard photodiodes. As such, this design development includes mechanical designs and drawings of

y = 121.59x - 2.9691

0

5

10

15

20

25

0 1/20 1/10 3/20 1/5 1/4

Max

Win

g Sp

read

An

gle

[deg

]

Optical Stop Diameter [in]

660 nm Laser Diode Max Wing Spread Angle vs. Optical Stop Diameter at 44.5 [in] Dist. to Wall



the vertical integrating sphere and laser diode heatsinks, electrical designs and drawings of the laser diode

boards and laser diode driver boards and design planning for the transimpedance amplifier.

Two tests were also completed: a test of the basic electronics functionality of the L660P120 laser diode,

the MLD203P2E laser diode driver, and the MLDEVAL board; and a test of the L660P120’s laser light

spread when unobstructed and affected by optical stops of various standard sizes. The basic electronics

test revealed that the L660P120 laser diode, the MLD203P2E driver, and the MLDEVAL board are all

functional (and that the MLDEVAL board need be very finely tuned to remain in an operational voltage

range). The test of the laser light’s spread revealed that the L660P120 laser diode produces a roughly-

circular spread of speckled incident light on a flat, perpendicular surface with a maximum main-diameter

spread angle of 18 degrees and a single wing with a maximum spread angle of 45 degrees. This test also

revealed that optical stops can greatly reduce the spread angles of the main-diameter and the wing.

References (This is an internal document. Formal list of references also available upon request)

Optical Payload Subsystem Design and Development for ORCASat – Peter Ogilvie

Airborne Laser for Telescopic Atmospheric Interference Reduction Payload – Alex Dokjnas

MECH 400 - Final Report UVic Satellite Design Payload – Gregory Perry, Roderick Gravouille, and

James Sease

ECE 490 – Progress Report – Evan Moore and Trevor Zakus



Appendices

Appendix A: Spring 2018 Optical Payload Design (HOMATHKO)

Figure 35: Homathko’s Optical Payload Design, isometric view

Figure 36: Homathko’s Optical Payload Design, front view

Figure 37: Homathko’s Optical Payload Design, right view



Appendix B: Summer 2019 Optical Payload Design (ORCASat)

Figure 38: ORCASat’s First Optical Payload Design, isometric view

Figure 39: ORCASat’s First Optical Payload Design, front view

Figure 40: ORCASat’s First Optical Payload Design, right view



Appendix C: Winter 2020 Optical Payload Design (ORCASat)

Figure 41: ORCASat’s Second Optical Payload Design, isometric view

Figure 42: ORCASat’s Second Optical Payload Design, front view

Figure 43: ORCASat’s Second Optical Payload Design, right view



Appendix D: Electrical Circuit Schematics

Figure 44: Laser diode heatsink circuit board schematic (designed by Trevor Zakus for ECE 490)

Figure 45: Laser diode driver circuit board schematic (designed by Evan Moore for ECE 490)



Figure 46: Temperature-monitoring circuit schematic (designed by Evan Moore for ECE 490)

Figure 47: Payload motherboard circuit schematic (designed by Evan Moore for ECE 490)



Appendix E: Test Plan Objectives To complete its primary functions (generate target light of two constant wavelengths and constant powers

in low earth orbit that can be observed by ground-based telescopes during an observation period, and

measure the optical power of the generated light onboard the spacecraft), mission requirements for

ORCASat’s optical payload were set to include:

• Minimum Optical Power Output of 80mW

• Wavelength drift maximum of 10nm

• Center Wavelength Determination of 0.25nm

• RMS power noise needs to be less than 1%

• Light Visible for an Observer at Sea Level Apparent Magnitude: 12 - 22

• 50 samples per second minimum for light measurements from the photodiode

• The laser needs to emit for minimum 2 seconds continuously without overheating

• The payload to be able to operate within -40 to +65 degrees Celsius

To verify that these mission requirements are met, a test plan is being developed for the Optical Payload.

First, the laser diode module’s operation and design will be tested. Testing of the entire Optical Payload

including the integrating sphere will be the subject of future documentation.

Laser Diode Module Test Plan Verification tests for laser diode module operation and design are outlined here, many of which are pulled

from Evan Moore and Trevor Zakus’ ECE 490 report. Full test procedures for each test will be the subject

of future documentation.

1. Basic Electronics Functionality

This first test will follow PCB population, and is comprised of several basic electronics checks, including:

• Laser diodes turn on and off.

• Laser diode driver power control is operational.

• Thermistor is reading temperature.

2. Basic Optical Properties of Laser Diodes

To examine the basic properties of the laser diodes used in this design, this test will include:

• Examining laser diodes’ bare light pattern (on the wall in a dark room).

• Examining laser diodes’ light pattern alongside basic optical stops of various sizes.

3. Optical Noise Measurement

• Examining the stability of the laser system by measuring the laser diodes’ output optical

power using an optical power meter to measure a high sample rate of light intensity. Note that

changes of a frequency lower than that which is measurable by the TIA sample rate would be

acceptable. Although this TIA threshold is currently unknown (the TIA has not yet been

designed), preliminary readings of the laser diodes’ optical noise are important.

4. Thermistor Calibration

• Calibrating the thermistor using high-quality temperature measurements in 0.5 °C steps.

5. Active Power Control Accuracy

• Examining the accuracy of the laser diode driver power measurement by sending a power

level to the digital to analog converter while measuring the laser diode driver’s power output

• Examining the responsiveness of the laser diode driver by measuring the output power of the

laser diode driver while changing its desired output power.



6. Temperature Gradient Between Laser Diode Case and Heatsink

• Examining the error between the temperature measured by the thermistor potted in the laser

diode heatsink and the temperature of the laser diode case (using a laser diode with a built-in

thermistor).

7. Wavelength Drift per Temperature Variation

• Examining the laser diodes’ emitted wavelength drift due to the laser diodes’ temperatures by

measuring the laser diodes’ output wavelength with a spectrum analyzer while

simultaneously measuring the laser diode heatsink’s temperature using its potted thermistor.

Ideally this test will be performed at each laser diodes’ maximum output power, but that may

be limited by available spectrum analyzers.

8. Failure of Laser Diode Driver

• Rigorously examining how Thorlabs laser drivers fail, and what makes them fluctuate.

9. Laser Diode Temperature-testing in Vacuum

• Examining the laser diode heat sink’s thermal response in vacuum by measuring its

temperature while operational in vacuum for the maximum operational time.



Appendix F: Unobstructed Laser Light and Effect of Optical Stops Photos

Figure 48: Incident laser light with no optical stop, featuring a 28” main diameter and an 18” wing, 44.5”

away.

Figure 49: Incident laser light with a 13/64" optical stop at 0.375", featuring a 12.5" main diameter and a

10" wing 44.5" away.


wing 44.5" away.



Figure 51: Incident laser light with a 11/64" optical stop at 0.375", featuring a 10" main diameter and a

8" wing 44.5" away.


wing 44.5" away.




wing 44.5" away.

Figure 54:Incident laser light with a 1/8" optical stop at 0.375", featuring a 7" main diameter and a 6.5"

wing 44.5" away.


wing 44.5" away.




wing 44.5" away.


wing 44.5" away.

Figure 58: Incident laser light with a 1/16" optical stop at 0.750", featuring a 2.5" main diameter no wing

44.5" away.

ORCASat Optical Payload

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A

UNLESS OTHERWISE SPECIFIED:DIMENSIONS ARE IN INCHESSURFACE FINISH:TOLERANCES: LINEAR: ANGULAR:

FINISH: DEBURR AND BREAK SHARP EDGES

NAME SIGNATURE DATE

MATERIAL:

DO NOT SCALE DRAWING REVISION

TITLE:

DWG NO.

SCALE:1:2 SHEET 1 OF 14

A4

WEIGHT:

ORCA PayloadSOLIDWORKS Educational Product. For Instructional Use Only.

Bill of Materials

ITEM NO. PART NUMBER DESCRIPTION QTY.

1 RotatedSecondHeatsink_Double_Down Laser Diode Heatsink 1

2RotatedSecondIntegrating sphere Front Double Down

Integrating Sphere Front Hemisphere 1

3 Rotatedlaser-socket Laser Diode Socket 2

4RotatedSecond Integrating sphere Back

Integrating Sphere Back Hemisphere 1

5 96126A121 Shoulder Screw 2

6 RotatedSecondL660P120-Solidworks Red Laser Diode 1

7 RotatedSecondL850P200-Solidworks IR Laser Diode 1

8 Rotated Support Ring Integrating Sphere Support Ring 1

9 Rotated Retainer Laser Diode Heatsink Retaining Ring 1

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:

ORCA Payload

0.003"

SOLIDWORKS Educational Product. For Instructional Use Only.

2.162

2.555

BHS2.362

A

A

M2.5 CLEARANCE8 PLCS 0.059

0.941

1.

929

SECTION A-ASCALE 1 : 1

SECTION A-ASCALE 2 : 1

Integrating SphereFront Hemisphere

Al 6061-T6

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


0°

22.5°

67.5° 112.5°

157

.5°

202.5° 225°

315°

337

.5°

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


0°

30°

150°

D

D E

E

0.250

0.0

20

30°

0.938 0

.087

SECTION D-DSCALE 1 : 1

0.020

30°

0.938 0.087

SECTION E-ESCALE 1 : 1

0.250

0.70 INC

H CLO

SE FIT

(LOC

ATIN

G FEA

TURE)

0.250

0.70

INC

H C

LOSE

FIT

(LO

CA

TING

FEA

TURE

)

0.003"

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


K

K

0.142

30°

0.938

0.0

67

0.0

87

SECTION K-KSCALE 1 : 1

0.625 INCH CLOSE FIT

(LOCATING FEATURE)

0.3

54 R0.12

1.0

69

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


1.9

29

2.

555

BHS R1.18

C

C

M2.5 CLEARANCE8 PLCS

0.059

2.

044

SECTION C-CSCALE 1 : 1

Al 6061-T6

Integrating Sphere Back Hemisphere

0.003"

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


0°

22.5°

67.5° 112.5°

157

.5°

202.5° 225°

315°

337

.5°

0.003"

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


2.054

2.565

2.713

BHS 2.362

LL

M2.5x0.458 PLCS

0 0.098 0.157 SECTION L-L

Integrating SphereSupport Ring

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


0°

22.5°

67.5° 112.5°

157

.5°

202.5° 225°

315°

337

.5°

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:

ORCA Payload

0.003"

SOLIDWORKS Educational Product. For Instructional Use Only.

1.25 INCHNOM.

0.000

0.236

0.500

0.236

0.500 0

0

.128

0.3

74

0.1

28

0.3

74

0.1

33

0.1

33

60° 0.069

0

0.648

1.052

0

0.1

4 0

.04

0.2

4 0

.51

0.6

1 0

.71

0.7

5

0.710

Laser Diode Heatsink

Al 6061-T6

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


4-40 UNC 2 PLCS

M3x0.5 2 PLCS

0.25 INCH CLEARANCELOOSE FIT2 PLCS

R0.063 FILLET

4 PLCS

0.232(6MM)

2 PLCS

0.177(4.5MM)THRU 2 PLCS

6MM CLEARNACE

LOOSE FIT

2 PLCS

NNOO

0

0.315 0.394 0.632 0.671

0.868 0.880

SECTION N-N

0

0.671

SECTION O-O

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


0.

625

0

0.319

0.015

0.003"

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


R0.123

R0.114

R0.073FILLET4 PLCS

0.136THRU2 PLCS

0.125 INCH CLEARANCE

LOOSE FIT

2 PLCS 0

0

.016

0

.031

0.1

28

0.1

23

0.0

16

0.0

31

0.1

28

0.1

23

0 0.016

0.236

0.236

0.016

0

0.09 0.13

Laser Diode Heat SinkRetaining Ring

0.003"

ABS PLASTIC

NOTE:-3D PRINTED ABS TO BE TESTED FOR THERMAL PROPERTIES.-3D PRINTED ABS DOES SATISFY NASA OUTGASSING REQ.

A A

B B

C C

D D

E E

F F

4

4

3

3

2

2

1

1

DRAWN

CHK'D

APPV'D

MFG

Q.A



NAME SIGNATURE DATE

MATERIAL:


TITLE:

DWG NO.


A4

WEIGHT:


PHYS 490 - wiki.heprc.uvic.ca

Documents

Transcript of PHYS 490 - wiki.heprc.uvic.ca