# Presentation: 668809

## SuperNova / Acceleration Probe

**June 28, 2001**

**Command and Data Handling System**

**SuperNova / Acceleration Probe**
**(SNAP)**

## 1 Generic C&DH Box with Mission-Unique Upgrades
Buffers/Multiplexers/Compressors Integrated in Readout Electronics
Real-Time Science Data Downlink
Store and Forward Spectrograph Data
Single-String (2 year) or Dual Redundant (5 year) Options

**Buffers/Multiplexers/Compressors Integrated in Readout Electronics**
**Real-Time Science Data Downlink**
**Store and Forward Spectrograph Data**
**Single-String (2 year) or Dual Redundant (5 year) Options**

**Command & Data Handling System****Overview**

## Command & Data Handling SystemDriving Requirements

**Launch:****	****October 2008**
**Orbit:****	****57 RE x 19 RE, 40****o**** incl**
**Life:****	****2 Years Minimum**
**	****	****5 years Goal**
**Science Data Acquisition Rate:****	****90 Mbps Peak**
**	****	****45 Mbps Average**

## Command & Data Handling SystemDerived Requirements

**Data Products (Data Reduction):****	****None**
**Data Compression:****	****Lossless Only**
**Telecommunication Contact Time:****	****80% of orbit**
**Telecommunication LOS Period:****	****24 hours **
**Real-Time Science Data Transmission:****	****All Instrument Data**
**Science Data Record and Playback:****	****Spectrograph Data Only**
**Spectrograph Data Storage:****	****74 Gbits**
**Simultaneous Record and Playback:****	****yes**
**Downlink Data Rate:****	****55 Mbps**

## Command & Data Handling System Science Data Reduction Analysis

_**Histogram Data Products**_
**Memory Array represents CCD pixel grid**
**1 Accumulator register for each pixel**
**1 Gpixel = 16 Gbit array (16 bits per register)**
**Rejected due to complications associated with**
**	****Cosmic Rays: False data spikes on CCD, data filter not feasible**
**	****Dithering: Spatial error on CCD**
**Lossy Data Compression also rejected**

## Command & Data Handling System Science Data Storage Analysis

_**100 % All Instrument Data Storage**_
**Science Data Acquisition Rate****	****45 Mbps**
**Housekeeping Data Acquisition Rate****	****16 kbps**
**Memory Error Detection and Correction Overhead (5%)****	**_**2 Mbps**_
**Total****	****47 Mbps**
**Data Storage Retention (8 hours during LOS)****	****1.4 Terabits**

## Command & Data Handling System Science Data Storage Analysis

**Command & Data Handling System Science Data Storage Analysis**

_**100 % All Instrument Data Storage (continued)**_
**1.4 Terabits SSR**
**2004 Rad-Hard DRAM Technology Projection: 64 Mbit or 256 Mbit**

**SSR with 64 Mbit DRAM**
**Size: 33 cm x 33 cm x51 cm**
**Mass: 30 kg**
**Power: 103 W**
**Cost: $3.1 M**

**SSR with 256 Mbit DRAM**
**Size: 33 cm x 33 cm x35 cm**
**Mass: 20 kg**
**Power: 70 W**
**Cost: $2.6 M**

## Command & Data Handling System Science Data Storage Analysis

_**100 % All Instrument Data Storage (continued)**_
**100 % All Instrument Data Storage rejected due to:**
**	****SSR mass, size, power, and cost**
**	****Relatively complicated operations**
**Alternative:**
**Downlink in real-time all science data while telecom is on-line (80%)**
**Store and forward only the Optical and NIR Spectrograph data**

## Command & Data Handling System Science Data Storage Analysis

_**100 % Spectrograph Only Data Storage**_
**Spectrograph Data Acquisition Rate****	****800 kbps**
**Housekeeping Data Acquisition Rate****	****16 kbps**
**Memory Error Detection and Correction Overhead (5%)****	**_**41 kbps**_
**Total****	****857 kbps**
**Data Storage Retention (24 hours during LOS)****	****74 Gbits**
**24 hour retention period derived from orbit and ground station location**

## Command & Data Handling System Downlink Data Rate Analysis

**Data Acquisition Rate:****	****45.2 Mbps**
**CCSDS Protocol and RS-Coding Overhead (15%):****	****6.78 Mbps**
**Stored Spectrograph Data Playback:****	**_**3 Mbps**_
**Total:****	****55 Mbps**
**74 Gbit Spectrograph Data Playback Time @ 3 Mbps:****	****6.6 hours**

##  Command & Data Handling System Selected Configuration and Rationale

** ****Command & Data Handling System Selected Configuration and Rationale**

**Flight Data System**

**Spacecraft Data Bus and Hard-Lines**

**Science Data**
**45 Mbps**

**X-Band Communication System**

**C&DH**
**Unit**

**Spacecraft Systems**

**Instrument**
**Electronics**

**S-Band Communication System**

**Command Uplink 2 kbps**

**Telemetry Downlink**
**1 kbps**

**Wideband Downlink**
**55 Mbps **

##  Command & Data Handling System Selected Configuration and Rationale

**8 Mbps**

**Telescope**

**NIR Spectrograph**

**Optical Spectrograph**

**NIR Imager**

**GIGACAM**

**Star Guider**

**Readout Electronics**

**Readout Electronics**

**Readout Electronics**

**Readout Electronics**

**Readout Electronics**

**Data Rate Buffer**

**Instrument Electronics**

**8 Mbps**

**200 Mbps**

**1 Gbps**

**8 Mbps**

**1**

**1**

**24**

**128**

**1**

**Multiplex and Compress**

**Data Rate Buffer**

**Data Rate Buffer**

**Data Rate Buffer**

**Data Rate Buffer**

**400 kbps**

**400 kbps**

**8 Mbps**

**40 Mbps**

**400 kbps**

**1**

**1**

**1**

**1**

**1**

**Multiplex and Compress**

**Multiplex and Compress**

**Multiplex and Compress**

**Multiplex and Compress**

**Fibre Channel Driver**

**Control**

**Bursts**

**Average**
**(double for peak)**

##  Command & Data Handling System Selected Configuration and Rationale

**C&DH Unit**

**Low Voltage Power Converter**

**S-Band Com Interface**

**Command  and Telemetry Lines**

**Backplane Data Bus**

**Spacecraft Data Bus**

**S**

**C&DH & ACS Processor**

**Wide-Band Data Router**

**Memory**
** ****74 Gbits**

**S-Band Uplink Downlink**

**C&DH Discrete Inputs and Outputs**

**S**

**Instrument Science Data**

**I**

**Q**

**KA-Band Com Interface**

## Command & Data Handling System RSDO Spacecraft Bus Accommodation

**1 RSDO spacecraft bus appears to meet the C&DH Requirements:**

|  | Science Data Acquisition Rate | Bulk Memory Size | Wide-Band Output Data Rate |
| --- | --- | --- | --- |
| C&DH Requirements | 45 Mbps  | 74 Gbits | 55 Mbps |
| X Bus | 576 Mbps | 200 Gbits | 320 Mbps |

## Command & Data Handling System Specifications and Cost Summary

_**Item**_**	****	**_**Mass kg**_**	**_**Power**_**	**_**Cost **_
**Single-String C&DH Unit*********	****12 kg****	****25 W****	**** **
**Dual-Redundant C&DH Unit**********	****24 kg****	****30 W****	**** **
**	*****   2 year life**
**	******  5 year life**
**	**

##  Command & Data Handling System Issues and Concerns

**No Data Retransmission Capability for Real-Time KA-Band Dropouts**