1. TRIO-CINEMA 1 UCB, 2/08/2010 Solar Array Kevin Jenkins Mechanical Engineering Space Sciences Laboratory University of California, Berkeley

2. TRIO-CINEMA 2 UCB, 2/08/2010 Solar Cell Agenda AGENDA Overview Requirements Design Test Results Development Plan Issues

3. TRIO-CINEMA 3 UCB, 2/08/2010 Overview Panels made from TASC cells will be placed on the outside of the satellite, as shown

4. TRIO-CINEMA 4 UCB, 2/08/2010 Requirements Level 3 Solar Arrays SAR-01Number of Panels 1U panels on +X, -X, +Z, -Z faces. 3x1U panels on +Y and -Y faces SAR-02Panel Size Each Panel covers a ~8x8cm area with ATJ cells with >80% packing factor SAR-03CellsCells shall be 27% efficient or better (prior to any losses) SAR-04StringsArray strings shall be 2-6 (TBR) cells in length SAR-05Blocking Blocking diodes and/or FETs shall be sued to prevent back- biasing shadowed cells. Blocking may be done on a per string or per panel basis - TBR SAR-06Cover Glass If the cells come without cover glass, some additional radiation shielding will be needed to get the cells to last at least 1 year with no more than 10% radiation losses. SAR-07Backwiring Cells shall be wired to minimize the generated magnetic torque by limiting the area of the current loop and inverting string geometry so strings cancel each-other. An illuminated panel shall generate no more than 1E-3Am2 SAR-08MassPanels shall weigh ~37g each

5. TRIO-CINEMA 5 UCB, 2/08/2010 Full PCB wiring view: Holds 24 cells 2 cells per string 1 Blocking diode per string of 2 cells Wired to minimize magnetic field generated: Current flows in small loops Flows in different directions on different layers Design

6. TRIO-CINEMA 6 UCB, 2/08/2010 Design Cells will be arranged as shown Each solar cell will have a temperature sensor on it to ensure predictable performance Tabs arranged as shown to accommodate screw holes They will be placed differently on different panels This one is for the 3x1U side

7. TRIO-CINEMA 7 UCB, 2/08/2010 Design Alternative: Clydespace Panel Advantages/Disadvantages: Clyde Array TASC Array Cost -+ Risk (Assembly and Coverglass) +- Education Value -+ Magnetic Cleanliness -+

8. TRIO-CINEMA 8 UCB, 2/08/2010 Design TASC Cells do not have a protective coverglass An encapsulant may be used instead Material is called CV10-2500 Silicone Based, by Nusil Low-outgassing (TML=.05%) Optically clear Radiation darkening still uncertain

9. TRIO-CINEMA 9 UCB, 2/08/2010 Design Scotchweld 1838 epoxy will hold cells on PCB during assembly More will be applied after for structural support Contacts between cell and PCB will be made with solder.

10. TRIO-CINEMA 10 UCB, 2/08/2010 Assembly Testing Assembly Procedure Testing: Reflow oven effectively melts solder between cell and substrate Epoxy holds well under heat, keeps cell in place Further testing awaits PCB Solder adheres better to PCB No way yet to test electrical performance for this design

11. TRIO-CINEMA 11 UCB, 2/08/2010 Assembly Testing Infra-red thermometer to control for possible variation of cell power under different temperatures Ambient lighting controlled for

12. TRIO-CINEMA 12 UCB, 2/08/2010 Electrical Testing Re-tested cells show good repeatability

13. TRIO-CINEMA 13 UCB, 2/08/2010 Development Plans Development ETU panel will be assembled February 2010 PCB will be fabricated Reflow procedure will be revised, taking into account any issues with new prototype Testing of panel will occur March 2010 As weather improves, electrical tests will be conducted with actual sunlight to achieve full-spectrum Fabrication of flight panels will take place summer 2010

14. TRIO-CINEMA 14 UCB, 2/08/2010 Issues Solar Cells Waiting on PCB to do more testing on assembly procedure Need to make sure that solder will not creep too much at higher temperatures We will research alternative solders, possibly containing silver for heat tolerance We’re not sure yet what type of temperature sensor will be used with the cells.