# Presentation: 194290

## SNAP baseline
Existing technologies
Improvements needed for SNAP
Scope of possible FNAL involvement

Highly elliptical orbit
2.5 Re x 25 Re
3 day cycle
85% data collection
~12 hrs in low orbit
   (5 hrs over Berkeley)

- Existing technologies
- Improvements needed for SNAP
- Scope of possible FNAL involvement
- Highly elliptical orbit
- 2.5 Re x 25 Re
- 3 day cycle
- 85% data collection
- ~12 hrs in low orbit
-    (5 hrs over Berkeley)

- SNAP Data Recorder

## SNAP Baseline

- “A solid state recorder – a shoebox”
- No moving (rotating) parts
- Lots of memory
- Radiation / space qualified
- Low power
- SNAP plans to transmit data in K band @ 150-300 Mbs with 6W transmitter.
- 375 Gbyte (Levi, DOE talk) might grow to ~500 Gbyte storage (expanded science).

## Memory technologies

- Memories
- Dynamic RAM
- Parasitic capacitance needs power to refresh
- Static RAM
- 2 transistors + 4 resistors FLIP-FLOP
- FLASH memories
- Floating gate with tunneling processes
- FeRAM
- Ferromagnetic crystal storage
- Holographic and other technologies
- Tape and disk recorders are candidates

## Some current missions

- Cassini
- Two SSRs each of 2.5 Gbit
- 640 4Mbit DRAMs
- Early 90’s technology => ’97 launch
- Multiple-bit upsets observed despite testing (architecture flaw)

- 3 control ASICs
- 120 DRAM/board
- Error detection and
-   correction circuitry

## Hubble Space Telescope
Reel-to-reel tape replaced by SSR
1.2 Gb -> 12 Gb
1440 16 Mbit DRAM
Two stacks of 10 (+2 spare) for 320 Mb packages (still 12500 chips for 500 GB)

Single event upsets observed
EDAC (Reed-Solomon scheme)
Two events where memory corrected but damaged
Kepler (earth size planets transiting stars)
Large CCD array, but only star’s pixels Xmit’d

- Reel-to-reel tape replaced by SSR
- 1.2 Gb -> 12 Gb
- 1440 16 Mbit DRAM
- Two stacks of 10 (+2 spare) for 320 Mb packages (still 12500 chips for 500 GB)
- Single event upsets observed
- EDAC (Reed-Solomon scheme)
- Two events where memory corrected but damaged
- Kepler (earth size planets transiting stars)
- Large CCD array, but only star’s pixels Xmit’d

- Some current missions

## Challenges for SNAP

- Amount of memory
- No examples of large (>>1 GB) SSRs found
- Moore’s Law growth. Need ~4000 x 1 Gbit
- Mass budget
- Boards with 1000’s of chips is several 10’s lbs
- Power budget
- Need more information
- Radiation tolerance
- Space qualification

## Radiation Tolerance

- Ionizing radiation small (<50 Krad)
- SEE (Single Event Effects) include many failure mechanisms
- SEU (Single Event Upset) can change state of a bit

- DRAM
- Sensitive
- area

- SRAM
- Sensitive
- area

## Radiation Tolerance

- FLASH memories
- Very thin oxides make FLASH susceptible
- Charge pump is the suspect for many failures
- Limited number of read/write cycles

## Space qualification

- Thermal-Vac
- Vacuum and Temperature extremes (-40 to +90 degC)
- Vibration facility
- Hard shake
- More Thermal-Vac and vibration testing after mount
- Room filled with engine noise simulation

- HST HOST
- Mission

## Space qualification

## Space qualification

## Space qualification

## FNAL Involvement

- Large robust memory is nicely associated with expanded science program of deep field sky survey
- Radiation issues (tie-in with shield) are already studied at FNAL
- Next steps
- Continue to get working knowledge
- Contact vendors
- Narrow technologies to working concept
- ASIC resources are possible

## Conclusions

- No clear technology solution
- High density, low power, radiation hard
- Flash memories x10 less power (big difference between 100 W and 1 kW)
- New concepts not ready for 1 Gb scale
- Dense technologies use smaller feature sizes that are more prone to some failures
- ASIC solution is possible, but could memories be made dense enough with accessible minimal feature sizes