Open Source DTN for ISS Payloads Concept Proposal, 05-Jun Open-source DTN communication software for ISS Payloads Kevin K. Gifford BioServe Space Technologies, University of Colorado 05 June 2013

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun Presentation Context and Outline ISS Payload Communications, Open Source DTN Overview of DTN Why important: ISS utilization, autonomous “lights-out” ops, efficient utilization of available bandwidth Increase in science and telemetry return; improved situational awareness Shared, cooperative communications for internationally-partnered exploration missions Tutorial / background on DTN communications History of DTN onboard the ISS: CGBA's, ESA QuickStart-A / OpsCom-1, SPHERES activities ISS-DTN Institutional DTN CR Payload, and NASA ISS Operations, DTN service provision strategies. Proposal: Provide open-standard, open-source (free software that can be modified and re-distributed) for the ISS payload community Provide a canonical configuration-managed open source repository of DTN payload software: support BCS, EXPRESS and PEHG, STELLA, TReK based payloads, and SSC users with DTN core and client software

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun Benefits of DTN for Payloads and Operations Delay, or disruptive, tolerant networks make use of automated store-and-forward techniques within the network in order to compensate for intermittent link connectivity typical of space & mobile environments. The reliable delivery of messages in such a “disconnected” network greatly benefits application layer operations, preventing data loss and associated labor costs.

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun Since the start of the space age, communications between spacecraft and ground stations has been characterized by simple, point-to-point data transmission. Problem Statement While Internet protocols this may work well for certain environments, they do not work well for many space-based and wireless mobile environments characterized by Asymmetric data rates, potentially high Bit error rates, intermittent link Connectivity (disruption), and long or variable transmission Delay. Existing Internet protocols have not been augmented for extension for space communications and rely upon several fundamental assumptions built into the terrestrial Internet architecture.

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun Enables the transition from point-to-point communications … to a truly networked Space Internet Why DTN is important for Disconnected Operations and Space Communications 5

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun DTN can significantly improve link utilization efficiency Fundamental observation: For ISS communications, prior to DTN deployment on the CGBA-4 and CGBA-5 payloads, the ability to automatically acknowledge telemetry successfully at groundside was unavailable. Thus, the two choices to manage payload telemetry transmission are to: (1)Transmit-in-the-blind and repeatedly resend telemetry (up to some frequency) to maximize the probability that the science and housekeeping telemetry is successfully received at the Control Center; or (1)Employ a manual operation where an operator manually uplinks acknowledgements to the ISS transmitting entity. Both options have costs and both are severely less-than-optimal. CU DTN G/W HOSC DTN G/W TDRS MSFC CGBA-5 Boulder

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun ISS Operational Gains Non-DTN Operations: All files downlinked repeatedly for configurable period (1-week default) to ensure all payload telemetry received despite disruptions in TDRSS coverage No file receipts uplinked acknowledgements (commands) are allowed by standard HOSC policy

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun ISS Operational Gains DTN Operations: Average number of file downlink transmissions to successfully receive and acknowledge is one with max of four with DTN file receipt acknowledgements This is unattended automated operations, i.e., operations personnel are not involved

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun ISS Operational Gains Payload Developer/Principal Investigator (PI/PD) resulting capabilities Reduction of the need for 24x7 availability of interfaces – Payload Operations Centers no longer are required to be “online” to receive payload telemetry – all payload telemetry can be retrieved at payload operator discretion and leisure Minimize the use of the current playback interface currently provided to payload developers leading to reduced operational planning requirements – no interfacing with the ISS Cadre required to retrieve any missed telemetry data Generic ISS-to-ground payload command and telemetry communications eliminates the need for PI/PD development of specific ISS payload command and telemetry systems

Open Source DTN for ISS Payloads Concept Proposal, 05-Jun ISS Operational Gains Benefits of ISS DTN Gateways for ISS networking and utilization Reduce/eliminate PI/PD development of ISS-to-ground communications software Provide Payload LAN DTN service provision and network to support advanced international networking, along with robotics payloads and experiments Minimize the need and costs for custom Payload Operations Control Centers, POCCs, to interface with ISS payloads; just use the Internet Optimize available bandwidth utilization for current ISS-to-Ground communications, and for the increase in bandwidth resulting from the ODAR and from Ku-forward Provide data redundancy onboard the ISS and at the HOSC via the DTN Gateways for improved data integrity and availability The ISS DTN gateway would be made available for the 18 internal ISS Payload Racks (7 ER, 5 Facility Racks, 3 Cold Storage Racks, 3 HRF Racks) and for international utilization