WHITE PAPER
Rad-tolerant storage
mrcy.com 4
Because every mission has a unique set of requirements,
the storage subsystems are tunable to balance power
consumption, ECC functions and storage capacity. Radiation
shielding is also a mission-specific option, customized in
conjunction with the mission's imaging system designers.
The NAND flash implementation is worth some discussion.
Flash memory designed specifically for rad tolerance has
significantly reduced per-chip storage capacity compared with
standard chip versions. For that reason, Mercury chose to use
industrial SLC NAND flash devices determined to be tolerant
to at least 30 krad, then added superior storage reliability
via mathematically rigorous horizontal Reed-Solomon ECC.
The NAND flash parts are screened in accordance with
NASA's EEE-INST-002 instructions, while each lot of NAND
parts undergoes radiation lot acceptance testing (RLAT)
and destructive physical analysis (DPA) before screening.
THE ADVANTAGES ARE CLEAR
Mercury's rad-tolerant storage product family is
unique in meeting the requirements of today's most
advanced satellite imaging programs, with a design
approach that will use tomorrow's technologies right
now to maintain that leadership. The performance
and operational advantages include:
Highest-density rad-tolerant storage – All form factors
contain a large amount of storage capacity in a small
form factor. For example, the 3U VPX RH3440 has 440
GB of data storage capacity in a 406 cm
3
package.
Compact and lightweight – Designed in a 3U form factor,
our SSDRs meet the needs of next-gen LEO satellites.
Extreme reliability – Mercury 's storage technology design
has no microprocessor or software, always potential failure
points. It uses a triple redundant RTG4 rad-tolerant FPGA to
control the NAND flash. Powerful ECC, capable of correcting
data from multiple NAND devices, and hot-swap replacement
of failing NAND devices add further layers of reliability.
Long-term mission support – Designed to meet the five-
year operational lifetimes of advanced imaging programs.
Constant capacity over the entire product life – Automatic
replacement of worn-out NAND blocks means the imaging
system always has the same view of storage capacity.
Standards-based solutions – Our SSDRs are packaged in 3U
VPX and 6U VPX form factors, not proprietary enclosures.
Continuing commitment – Mercury has not created a one-off
product but rather a product family with an evolving roadmap
to deliver the most innovative space technology solutions.
Other Applications Also
Need Radiation Tolerance
Satellite imaging is not the only application
set requiring rad-tolerant data storage.
High-altitude airplane imaging is a similar,
but distinct, area. Flights at 40,000 feet or
more are often used to collect extremely
detailed images of ground artifacts —
images which are stored on the aircraft
until it returns to its base. At 40,000 feet,
cosmic radiation is not at space levels but
it is still intense and a serious issue that
must be addressed. Mercury's rad-tolerant
storage subsystems meet the need, as
off-the-shelf, standards-based solutions
that are lightweight and low-power.
Even on the Earth's surface, medical
imaging and nuclear power generation
create environments with high levels
of radiation. Rad-tolerant storage from
Mercury is a reliable way to ensure data
integrity for any data collected and
stored within those environments.
RH3440 Radiation-Tolerant SSDR
