<s>
The	O
NASA	O
Standard	O
Spacecraft	O
Computer-1	O
(	O
NSSC-1	B-Device
)	O
is	O
a	O
computer	O
developed	O
as	O
a	O
standard	O
component	O
for	O
the	O
MultiMission	O
Modular	O
Spacecraft	O
at	O
the	O
Goddard	O
Space	O
Flight	O
Center	O
(	O
GSFC	O
)	O
in	O
1974	O
.	O
</s>
<s>
The	O
computer	O
had	O
18	O
bit	O
wide	O
core	B-General_Concept
memory	I-General_Concept
or	O
plated	B-General_Concept
wire	I-General_Concept
memory	I-General_Concept
;	O
up	O
to	O
64	O
k	O
.	O
18	O
bits	O
was	O
chosen	O
because	O
it	O
gave	O
more	O
accuracy	O
(	O
x4	O
)	O
for	O
data	O
over	O
a	O
16	O
bit	O
machine	O
.	O
</s>
<s>
Floating	B-Algorithm
point	I-Algorithm
arithmetic	I-Algorithm
was	O
not	O
supported	O
.	O
</s>
<s>
The	O
machine	O
used	O
diode	B-General_Concept
–	I-General_Concept
transistor	I-General_Concept
logic	I-General_Concept
,	O
the	O
lowest	O
power	O
parts	O
available	O
at	O
the	O
time	O
on	O
the	O
preferred	O
parts	O
list	O
;	O
initially	O
fabricated	O
from	O
1700	O
SSI	O
(	O
NOR	O
gate	O
)	O
packages	O
,	O
the	O
later	O
AOP	O
was	O
implemented	O
using	O
69	O
MSI	O
(	O
medium-scale	O
integration	O
)	O
TTL	B-General_Concept
chips	O
from	O
Harris	O
.	O
</s>
<s>
The	O
NSSC-1	B-Device
was	O
implemented	O
by	O
IBM	O
using	O
TRW	O
versions	O
of	O
the	O
Harris	O
chips	O
.	O
</s>
<s>
The	O
NSSC-1	B-Device
had	O
an	O
assembler/loader/simulator	O
toolset	O
hosted	O
on	O
Xerox	O
XDS	B-Device
930	I-Device
(	O
24	O
-	O
bit	O
)	O
mainframe	B-Architecture
.	O
</s>
<s>
Later	O
,	O
the	O
Software	O
Development	O
and	O
Validation	O
Facility	O
(	O
SDVF	O
)	O
added	O
a	O
flight	O
dynamics	O
simulator	O
hosted	O
on	O
a	O
PDP-11/70	O
minicomputer	B-Architecture
.	O
</s>
<s>
A	O
purpose-built	O
NSSC-1	B-Device
Flight	O
Executive	O
was	O
developed	O
for	O
use	O
on	O
the	O
Solar	O
Maximum	O
Mission	O
(	O
SMM	O
)	O
and	O
subsequent	O
flights	O
.	O
</s>
<s>
It	O
used	O
medium	O
scale	O
integration	O
transistor-transistor	B-General_Concept
logic	I-General_Concept
(	O
TTL	B-General_Concept
)	O
.	O
</s>
<s>
In	O
the	O
1980s	O
the	O
RCA	B-General_Concept
1802	I-General_Concept
was	O
used	O
for	O
many	O
missions	O
—	O
like	O
Galileo	O
.	O
</s>
<s>
Before	O
the	O
RAD	O
family	O
of	O
32	O
bit	O
CPUs	O
were	O
used	O
in	O
space	O
missions	O
,	O
the	O
MIL-STD-1750A	B-General_Concept
(	O
a	O
CPU	O
that	O
could	O
run	O
modern	O
applications	O
)	O
saw	O
substantial	O
use	O
.	O
</s>
<s>
Since	O
the	O
arrival	O
of	O
the	O
IBM	B-Device
RAD6000	I-Device
in	O
the	O
2000s	O
and	O
the	O
RAD750	B-Device
in	O
the	O
2010s	O
,	O
using	O
the	O
NSSC-1	B-Device
has	O
become	O
unthinkable	O
.	O
</s>
