Spacecraft solar array design to control differential charging

{
  "publication_number": "US5919316A",
  "country": "US",
  "kind": "A",
  "title": "Spacecraft solar array design to control differential charging",
  "abstract": "Numerous undesirable prior art epoxy beads or pads of metallization, employed to prevent unacceptable electrostatic charge buildup upon the solar cell coverglasses of solar cell array panels deployed in outer space, are eliminated by causing the charge conducting semiconductive coverglass layers to be wrapped around edge portions of each coverglass, to readily facilitate charge drainage of the electrostatic charge buildup.",
  "claims": [
    "1. Solar cell apparatus comprising: (a) an array of photocells; (b) a plurality of photocell protective coverglass members, each member having an edge portion and having an upper light transmissive charge conducting semiconductive layer thereon; (c) a plurality of interconnect members each electrically coupled between photocells of said array; and (d) wherein each coverglass member has its charge conducting semiconductive layer wrapped around the edge portion of each coverglass member and in electrical contact with an associated interconnect member.",
    "2. The apparatus of claim 1 wherein said charge conducting semiconductive layer is coated upon the edge portion of said coverglass member.",
    "3. The apparatus of claim 1 wherein said charge conducting semiconductive layer comprises a coating of indium tin oxide.",
    "4. The apparatus of claim 2 wherein said charge conducting semiconductive layer comprises a coating of indium tin oxide.",
    "5. Solar cell apparatus comprising: (a) an array of serially connected photocells, each photocell having an upper electrode of a first polarity and a lower electrode of a second polarity opposite said first polarity; (b) a plurality of protective coverglass members, each member having an edge portion, each coverglass member being positioned over an associated photocell and having an upper light transmissive charge conducting semiconductive layer thereon; (c) a plurality of interconnect members each electrically coupled between adjacent pairs of photocells to form said array and each having a first portion connected to the upper electrode of a particular photocell and a second opposite portion connected to the lower electrode of an adjacent photocell to connect said photocells in series; and (d) wherein each coverglass member has its charge conducting semiconductive layer wrapped around the edge portion of each coverglass member and in electrical contact with an associated interconnect member.",
    "6. The apparatus of claim 5 wherein said charge conducting semiconductive layer is coated upon the edge portion of said coverglass member.",
    "7. The apparatus of claim 5 wherein said electrodes are metallic layers.",
    "8. The apparatus of claim 6 wherein said electrodes are metallic layers.",
    "9. The apparatus of claim 5 wherein said charge conducting semiconductive layer comprises a coating of indium tin oxide.",
    "10. The apparatus of claim 6 wherein said charge conducting semiconductive layer comprises a coating of indium tin oxide.",
    "11. Solar cell apparatus comprising: (a) an array of photocells; (b) a plurality of protective photocell coverglass members, each member having an edge portion, and each coverglass member having a light transmissive charge conducting semiconductive layer thereover; (c) a plurality of conductive interconnect members electrically coupled between photocells; and (d) wherein each coverglass member has its charge conducting semiconductive layer wrapped around the edge portion of each coverglass member for electrically contacting an interconnect member.",
    "12. The apparatus of claim 11 wherein said charge conducting semiconductive layer is coated upon the edge portion of said coverglass member.",
    "13. The apparatus of claim 12 wherein said charge conducting semiconductive layer comprises indium tin oxide."
  ],
  "description_excerpt": "Arrays of numerous solar cells are affixed to panels mounted upon satellites in order to convert visible light emitted by the sun into electrical power. When such satellites operate at altitudes in the range of one to ten earth radii, the natural plasma environment may deposit electric charge on the cell protective coverglasses affixed to upper surfaces of the solar cells. The electrons at these altitudes are extremely energetic and a large amount of charge may accumulate, possibly enough to charge the coverglasses to 20,000 volts. This exceeds the voltage at which electrostatic discharging is known to occur, as the observed discharge threshold is about 1000 volts.\n\nTo prevent the production of voltages exceeding the discharge threshold, an indium tin oxide (ITO) layer is typically deposited upon the upper or space-facing side of each coverglass, and the ITO layer must be electrically grounded to prevent excessive charge buildup and detrimental discharges. However, there are between 5000 and 20,000 solar cells and associated coverglasses on each communication satellite. If any coverglass grounding connection fails, by becoming an electrically open circuit, the coverglass to which it attaches can build up to a voltage that exceeds the discharge voltage to produce unacceptable performance or cell damage. Two types of grounding techniques, to be described below, have been employed for preventing the destructive charge buildup on the coverglasses. These techniques add hundreds of hours of labor cost to the manufacturing cost of every conductively coated solar array.",
  "cpc": [
    "H10F 19/902",
    "B64G 1/443",
    "H10F 19/80",
    "Y02E 10/50"
  ],
  "ipc": [
    "H01L 31/048",
    "H01L 31/05"
  ],
  "assignees": [
    "United States Department of the Air Force"
  ],
  "inventors": [
    "Alexander Bogorad",
    "Charles Kenneth Bowman, Jr.",
    "William Raymond Krummann",
    "William Richard Hart"
  ],
  "filing_date": "1997-06-27",
  "publication_date": "1999-07-06",
  "grant_date": "1999-07-06",
  "priority_date": "1997-06-27",
  "application_number": "US-88468397-A",
  "family_id": "25385134",
  "cited_by_count": 54,
  "citations": [
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    "US3527619A",
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    "JPS60783A",
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    "US5620904A"
  ]
}