Automated File Transfer and Storage Management Concepts for Space

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

7. Target Mission • 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 2004 Space Internet Workshop

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

11. Calculated Transfer Times • Based on previous MDP performance measurements* (using 1 Mbyte files) Phase IPhase IIPhase IV 0 BER 23 min 82 min 221 min 1E-8 23 min 82 min 221 min 1E-7 26 min 91 min 246 min 1E-6 43 min 152 min 409 min 1E-5 60 min 217 min 508 min * Refer to "Characterization data for MDP, 2001" http://ipinspace.gsfc.nasa.gov/documents/report_2001_09_29_thru_31.wbk 2004 Space Internet Workshop

12. Projected Phase I Storage Utilization 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% 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 2004 Space Internet Workshop