1. Automated File Transfer and Storage Management Concepts for Space Gary Meyers - GSFC Ed Criscuolo - CSC Keith Hogie - CSC Ron Parise - CSC Revised 6/14/2004

2. 6/9/2004 2004 Space Internet Workshop 2 Overview Introduction Concepts Testbed Characteristics & Parameters Target Mission Testbed Architecture & Operation Planned simulations Results Conclusion & Future Efforts

3. 6/9/2004 2004 Space Internet Workshop 3 Introduction The purpose of this project was to validate and demonstrate the use of an IP-based, NAK-oriented, reliable file delivery protocol to meet a space mission's data delivery and storage management requirements for onboard stored data. To this end, we built a Data Delivery Simulation Testbed and simulated a real, upcoming mission.

4. 6/9/2004 2004 Space Internet Workshop 4 Concepts Instruments generate onboard data as streams of UDP packets. Replace onboard "Tape Recorder" paradigm with a file system using random-access files for stored data collection. Use IP-based standard "off-the-shelf" file delivery protocols for error-free transfer of stored data. Use file-level acknowledgements to automate the management of onboard storage space. Trade retransmissions and/or application-level FEC for BER.

5. 6/9/2004 2004 Space Internet Workshop 5 Testbed Characteristics Simulated instrument & housekeeping data generation Automated onboard data storage management Adjustable Space/Ground link characteristics Ground system receipt of all collected data The simulation testbed must be highly parameterized in order to accommodate changing requirements and investigate "What if" scenarios.

6. 6/9/2004 2004 Space Internet Workshop 6 Testbed Parameters Orbital Period Contact Time Separate Data Rates for Instruments and S/C Houskeeping Collection Time Per Data File Onboard storage cache size Downlink Data Rate Uplink Data Rate Link Delay Link Bit Error Rate

7. Revised 6/14/2004 2004 Space Internet Workshop 7 MMS (Magnetospheric MultiScale) chosen Orbit Characteristics –4-spacecraft constellation –Tetrahedral configuration –Highly elliptical orbit –4 mission phases, with orbital periods from 1 to 10 days Link Characteristics –Downlink rate =2 Mbits/sec –Uplink Rate = 2 Kbits/sec –Prop. Delay = 25 mS - 215 mS –One contact (per S/C) per orbit, close to perigee Data Rates (per S/C) –Aggregate Rate: 25 Kbits/sec continuously –4 Instruments: 10, 5, 5, 3 Kbits/sec –S/C Housekeeping:2 Kbits/sec Target Mission

8. 6/9/2004 2004 Space Internet Workshop 8 Testbed Architecture Inst 1 10 kbps Inst 2 5 kbps Inst 3 5 kbps Inst 4 3 kbps Spacecraft C&DH UDP Capture UDP Capture UDP Capture UDP Capture MDP Server Router Channel Simulator Router Ground System MDP Client Houskeeping 2 kbps UDP Capture Hot Directory Outbox Simulated Space Link: Delay and BER @ 2.0 Mbps Orbit Simulator Pause / Resume Data Archive Data Collection Inbox

9. 6/9/2004 2004 Space Internet Workshop 9 Testbed Operation UDPCapture continuously transforms data streams of UDP packets into discrete data files onboard. Data files are moved to MDP's hot directory when completed. Orbit simulator enables MDP server during contact passes. When enabled, MDP Server automatically sends any new files that have appeared in the hot directory, and manages onboard data storage space. Channel simulator hardware introduces propagation delay and bit errors. MDP Client reliably receives data files, automatically requesting retransmission of any bad packets. Files are moved to archive when complete.

10. 6/9/2004 2004 Space Internet Workshop 10 Planned Simulations Downlink Data Rate: 2 Mbps Uplink Data Rate: 2Kbps Link Prop. Delay: 25mS (Phase I & II), 215mS (Phase IV) BER: 0, 1E-8, 1E-7, 1E-6, 1E-5 Orbital Periods: 24 hrs (Phase I), 4 days (Phase II), 10 days (Phase IV) Inst/Hk Data Rates: 10, 5, 5, 3, 2 Kbps (25 Kbps total) Collection Time Per Data File (each instrument) : 3 hrs

11. 6/9/2004 2004 Space Internet Workshop 11 Calculated Transfer Times Based on previous MDP performance measurements * (using 1 Mbyte files) Phase IPhase IIPhase IV 0 BER23 min82 min221 min 1E-823 min82 min221 min 1E-726 min91 min246 min 1E-643 min152 min409 min 1E-560 min217 min508 min * Refer to "Characterization data for MDP, 2001" http://ipinspace.gsfc.nasa.gov/documents/report_2001_09_29_thru_31.wbk

12. 6/9/2004 2004 Space Internet Workshop 12 Projected Phase I Storage Utilization

13. 6/9/2004 2004 Space Internet Workshop 13 Results To date, the Phase I simulations have been run. Initial real-time run at 0 BER for 4 days –Transfer times matched analytically derived values. –Storage utilization matched analytically derived values to within 1% Similar results for BERs of 1E-8 & 1E-7 At BER of 1E-6 –Transfer times were slightly better than predicted –Storage utilization matched predicted within 1% 30 day run at BER of 1E-5 –Transfer times were 30% better than predicted (43 min vs 60 min) –Storage utilization matched predicted within 1%

14. 6/9/2004 2004 Space Internet Workshop 14 Conclusion & Future Efforts Conclusion –An IP-based, NAK-oriented, reliable file delivery protocol can meet MMS mission's Phase I data delivery and storage management requirements for onboard stored data. Future Efforts –Vary MDP block size from 1024 to 1500 and characterize the effect on goodput –Add pro-active application-level FEC to reduce retransmissions at BER of 1E-5 and characterize the effect on bandwidth utilization