IEEE - Aerospace and Electronic Systems - May 2021 - 51

Bai et al.
Table 2.

Output Current Changes for the SA of the TTS-5 During the Period of a Year and a Half
No.

Time of
occurrence

Steady
current
before falling
(A)

Steady
current
after falling
(A)

String number change
(bar)

Estimated single string
current(A)

1

2018-06-15

26.592

26.066

52!51

0.511

With seasonal changes, the steady current gradually rises from 26.066 to 26.658 A
2

2018-09-17

26.658

26.132

51!50

0.523

With the season changes, the steady current gradually rises from 26.132 to 26.691 A
3

2018-11-5

26.691

26.164

50!49

0.534

With seasonal changes and the third drop recovery, the steady current gradually rises from 26.164 to 27.448 A
4

2018-12-20

27.448

26.362

50!48

0.549

5

2019-01-03

25.770

25.210

48!47

0.537

6

2019-02-17

25.243

24.717

47!46

0.537

FAILURE CAUSE ANALYSIS

ANALYSIS AND DETERMINATION OF FAILURE CAUSES

STRUCTURE OF TTS-5 SA CIRCUIT
TTS-5 SA adopts a double-wing design and each wing has
two panels, and each panel is equipped with one SSA, as
shown in Figure 2. The þX wing inner panel, þX wing
outer panel, -X wing inner panel, and -X wing outer panel
are indicated with the SSA-1, SSA-2, SSA-3, and SSA-4,
respectively. The design uses high-efficiency gallium arsenide triple junction solar cells with a size of 80.0 mm Â
40.0 mm.
The single-wing SA circuit is composed of two
SSAs with the same design. Its power output is fed into
the satellite body by a terminal power connector which
is connected to on-panel connector through interpanel
cables. The schematic diagram of single-wing SA circuit
connection is shown in Figure 3. The SSA consists of
13 strings of solar cells in parallel and each string is
formed by 30-34 solar cells in series. Each string of
solar cells is connected in series with one isolation
diode. The physical photo of each single-panel SA is
shown in Figure 4, including the front and back pictures.
From Figure 4(a), we can see that each SSA is
composed of 424 solar cells.

Through the analysis of the SA circuit on-orbit failure
phenomenon and the re-examination of the SA
manufacturing process, the components and materials
used in the power circuit, the manual operation process
and the ground test result, the possible failure causes are
listed as shown in Table 3, including 3 classifications of
15 possible failure causes. The possible failures for the
three categories in the table are analyzed as follows.

SA CIRCUIT SHORT
Since the solar cell strings in each panel are output in parallel to the on-panel and interpanel power connector and

Figure 2.

Figure 3.

TTS-5 SA layout.

Schematic diagram of single-wing SA circuit connection.

MAY 2021

IEEE A&E SYSTEMS MAGAZINE

51



IEEE - Aerospace and Electronic Systems - May 2021

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