Viewgraphs on optical disk technology - spaceflight optical disk recorder (SODR) are presented. Topics covered include: SODR; key technologies; disk drive; and system concept

Rinsland, Pamela

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NASA Technical Reports Server

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LaRC TECHNOLOGYFORSPACE STATION
EVOLUTION
OPTICALDISKTECHNOLOGY
SPACEFLIGHTOPTICALDISK RECORDER
PAMELARINSLAND
NASA LANGLEY RESEARCH CENTER ¢D ' _',,
I'
I
January 16, 1990 "<__
SPACEFLIGHT OPTICAL DISK RECORDER
https://ntrs.nasa.gov/search.jsp?R=19930018521 2020-03-24T07:33:27+00:00Z
A NASA programto develop a high performance (high rate, high capacity) rewriteableoptical disk
recorder focused on use aboard unmanned polar orbiting platforms is underway at Langley
Research Center. An expandablesystem concept is proposed consistingof multiple drive modules
and a modularcontroller.System goals are 160 gigabyte capacity at up to 1.2 gigabits per second,
concurrent I/O, varying data rates, and five year operating life in orbit. Drive performance goals are
10 gigabyte capacity, 300 megabit/secondtransfer rate, 101° corrected BER and 250 millisecond
access time.
Although developmentis currently focused on Eos polar orbiting platforms,the SODR is an enabling
capability for many future missions, such as Space Shuttle and Space Station Freedom payloads,
Mars Rover,and polar and geostationaryorbiting platforms.A possible Space Station applicationfor
SODR is that of a dedicatedresourceto store the high speed optical data recordedand transmitted
from microgravity science experiments.Surveys conducted for a workshop sponsored by NASA-
Lewis in May 1988 show that a minimallyconfigured SODR can meet the requirementsof manyof
,_ the investigators.¢.o
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3.1-SPACEFLIGHTOPTICALDISKRECORDER(SODR)
OBJECTIVE
DeVelopanddemonstratecomponentsand subsystemsrequiredto providehigh-performance(highrate, highcapacity)
randomfile accessstoragesystemsbased onerasableopticaldisk technologyfor futurespaceflightmissions. This
includesdevelopmentof magneto-opticdisk media,diode laserarray,write/read/eraseelectro-optichead,diskdrive
unlt_and systemcontroller.
DESCRIPTION
Keytechnologiesthat formthe basis for the systemare14-inchmagneto-opticmedia,9-elementdiode laserarrays,
multi-trackelectro-optichead,and versatilesystemcontroller. The arealdensity (bit/area)of opticalmedia,is projected
to beeightto twentytimesthat of magneticmedia. The SODRgoal is 10gigabit perdisk. The useof a diodearray
and supportingelectro-opticheadto write, read,anderaseeight simultaneousdata trackson eachsurfaceprovides
highdata rate. Theper headgoal is 150 megabits/secor 300 megabit/drive.The conceptis a dual-sideddisk, two
heads,and supportingelectronicsinto a diskdrive package. An associatedmodularcontrolleris to bedevelopedto
producea configurable,expandablesystemwhichcanprovideupto onegigabit/secratesand 1.2terabitcapacities.
NASARATIONALEANDBENEFIT
Highperformancerandomfileaccessstorageis anenhancingand enablingcapability. Thecurrentprogramfocusis
applicationaboardPolarOrbitingPlatformsin supportof the EarthObservingSystem. Highperformanceoptical
recordinghaspotentialpayoffto manymajorNASAprogramsincludingthe SpaceTransportationSystem,Space
Station,includingGEOand PolarPlatforms,SpaceScienceand Exploration(e.g.,MarsRoverand LunarBase). There
arepotentialbenefitsto DoDspaceprograms,groundbasedGovernmentand commercialprograms,andthe
establishmentof nationalleadershipin criticaltechnologyareas.
STATUS/ ACCOMPLISHMENTS
Feasibilitywasdemonstratedin the lab in 1988. Thisyear the SODRprogramhasdevelopeda new laserstructure,
deliveredimprovedlaserswith 100 hour burnin, completedpreliminaryenvironmentaltestingof aluminumand glass
mediawithglassselectedasthe newbaseline,continuedcharacterizationand enhancementof the breadboarddrive
redefinedgoalsof a drivebrassboardreflectingDoDparticipation,establishedrequirementsand initiatedbreadboard
controllerdesign.
TechnicalContact:Tom Shull,LaRC,(804)864-1874(FTS928-1874)
The SODR program is sponsored by NASA's Office of Aeronautics and Space Technology and
managed by Langley Research Center. The objective is to develop and demonstrate the
technology,componentsand subsystems needed to achieve rewriteable optical disk mass storage
systemsfor space flight applications. The fundamental elements associated with this development
include the following: a) 14 inch dual-sided magneto-optic (MO) media, b) independently
addressable10-elementsolid state laser diode arrays, c) an eight data track electro-optic(EO) head
and d) electronicand mechanicaldrive subsystems.
Media studies have addressed the MO performance and suitability of glass versus aluminum
substratesfor harsh environments.Tests includedvibration, thermal cycling and outgassing.A blank
glass disk survived62 G rms randomvibration. Results indicate that glass is the preferredsubstrate
from both a performanceand cost viewpoint.
Laser developmentis focused on longevityand yield improvements.This includesfine tuning of the
laser structure and process refinement.Conversionto a new growth technique is being considered.
Techniquesare being studied to stabilize the lasing frequencythat can shift due to optical feedback
and aging.
The current spot geometry and spacing on the 14 inch disk support a capacity of 5 gigabytes per
side. The disk is formatted in a continuousspiral consisting of preformattedpermanent pilot track
that contains the radius (track number) identification data. This enables closed loop recordingand
playback that cannot be achieved with a concentric ring pattern. The permanent pilot track lies in
the center of a data band of eight rewriteabletracks 1.4 l_m apart. There is a 2.1 l_m guard band
betweendata bands to accommodatethe laser's 0.7 l_mspot diameter.
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_a._C_ KEYTECHNOLOGIES
i--
PERMANENTPILOTTRACK|/EIGHTDATATRACKS
_o
1DIODEARRAY
ELECTRO-OPTICHEAD
14-INCH
REWRITEABLE
MEDIA
SPACEFLIGHTOPTICALDISKRECORDER
Each SODR drive contains one 14" dual sided storage disk. The concept of a storage module
refers to two drives mountedwith counter rotating disks for angular momentum compensation.One
disk surface and its associated hardwareare referred to as a device (two devices perdrive). In the
current design the device is the minimum functionalunit. The minimumdeliverablephysicalunit is a
drive. The physical device contains the media and its supporting mechanisms.This includes the
optical heads, rotating disks, photodetectors,and the support subsystems (mechanical,optical and
electronic) needed to read or write information on the media. The goal for each drive is 10
Gigabytes of data capacityand 300 Mbpsdata throughput.
Drive specific functions required to transfer data from the user to the medium will be performed
within the storage module. These include sector mapping, data encoding, error detection and
correction (EDAC), buffering, overhead formatting,and command interpretations(seek, read, write
and erase).
_. The physical characteristicsof the projectedflight drive (dual device and device controller)are as
follows:
DEVICE CONTROLLER
SIZE: 3/4 FT 1/4 FT
WEIGHT: 45 LBS 15 LBS
POWER:Write 150 50 W 50 W
Write 300 70 W 100 W
Read 150 75 W 50 W
Read300 130 W 100 W
Erase300 70 W 0 W
ANGULARMOMENTUM:1 FT-LB-S
OVERALL DIMENSIONS:15.3"x 6.5" x 17.9"
DISK DRIVE
ELECTROOPTICHEAD
(SURFACE1}
ELECTROOPTICHEAD
(SURFACE2)
PERFORMANCEGOALS
10 GIGABYTE CAPACITY
300 MEGABITPERSECOND
14,.,M01rtlSl( 250 MILLISECONDACCESS
(TWO SURFACES)
The SODR is an expandable modular system which consists of a modular SODR Controller and
multiplestorage modules. Current plans are to design and build the SODR Controllerat LaRC and
to obtain the storage module design and developmentthrough outside sources. The RODR can be
modularly configured to provide up to 1.8 gigabits per second data transfer rate and up to 160
gigabytecapacity.
The primaryfunctional requirements of the SODR Controller are flexibility, high data rate, high
capacity, simultaneous I/0 through multiple ports, random access to files, and high reliability.
Flexibility will be provided by the system's modularity that allows the system to be configured to
meet different application requirements. Random access to data is an inherent feature in disk
storage systems. This feature will be provided by the controller in the form of random access to
files. The primary goals for system reliability include up to 1012 corrected BER and a minimum of
two to five years operating life in orbit.
The SODR Controllerwill perform standard data transfer functions such as directory management,
resource allocation and scheduling that remove the user from the physical details of the storage
modules. There are differences between the SODR Controller and other high performance
controllers.The SODR Controller also provides higher and variable data transfer rates, contains a
greater numberof modules (more than eight), and supportsdynamic reconfiguration,fault tolerance,
adaptablefile managementphilosophy and reprogrammablesystem algorithms. Also, the command
and data ports are separated to achieve the desired reconfigurabilityand data throughput.
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_a_ SYSTEM CONCEPT
DISK DRIVE
DISK DRIVE
ELECTRONICS
CONTROLLER
STORAGE MODULES
SPACEFLIGHTOPTICALDISK RECORDER
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CONCLUSION
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DISK RECORDERHAVE BEEN
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__" . PROGRAMSCHEDULECAN BE MET WITH
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SPACEFLIGHT OPTICAL DISK RECORDER


Optical Disk Technology Spaceflight Optical Disk Recorder (SODR)

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