Known Knowns and Unknowns: Near-realtime Earth Observation Via Query Bifurcation in Serval
Known Knowns and Unknowns: Near-realtime Earth Observation Via Query Bifurcation in Serval
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2024
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通讯作者：
Bill Tao;Om Chabra;Ishani Janveja;Indranil Gupta;Deepak Vasisht
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作者：
Bill Tao;Om Chabra;Ishani Janveja;Indranil Gupta;Deepak Vasisht
在近地轨道上的地球观测卫星越来越接近对地球的近连续成像。今天，这些卫星每隔几个小时就会捕捉到地球各个部分的图像。然而，网络功能还没有跟上，在将这些图像传回地球时可能会延迟几小时到几天。虽然这种延迟对于诸如土地覆盖图、作物类型识别等延迟容忍应用程序是可以接受的，但对于诸如森林火灾探测或灾害监测等延迟敏感应用程序是不可接受的。通过利用卫星和地面站上新兴的计算能力，我们设计了几个能够实现对延迟敏感应用的地球图像的近实时洞察，尽管存在网络瓶颈。我们工作的主要挑战来自卫星有限的计算能力和可用的电力资源。我们通过利用卫星轨道的可预测性，在卫星和地面站之间进行分岔计算来解决这一挑战。我们使用轨迹驱动模拟和硬件模拟对数据集进行了评估，该数据集包含由近200颗卫星组成的Planet Dove星座捕获的1000万张图像。几个将高优先级查询的端到端延迟从71.71小时（由目前的技术状况导致）减少到2分钟，并将第90百分位数从149小时减少到47分钟。
Earth observation satellites, in low Earth orbits, are increasingly approaching near-continuous imaging of the Earth. To-day, these satellites capture an image of every part of Earth every few hours. However, the networking capabilities haven’t caught up, and can introduce delays of few hours to days in getting these images to Earth. While this delay is acceptable for delay-tolerant applications like land cover maps, crop type identification, etc., it is unacceptable for latency-sensitive applications like forest fire detection or disaster monitoring. We design Serval to enable near-realtime insights from Earth imagery for latency-sensitive applications despite the networking bottlenecks by leveraging the emerging computational capabilities on the satellites and ground stations. The key challenge for our work stems from the limited computational capabilities and power resources available on a satellite. We solve this challenge by leveraging predictability in satellite orbits to bifurcate computation across satellites and ground stations. We evaluate Serval using trace-driven simulations and hardware emulations on a dataset comprising ten million images captured using the Planet Dove constellation comprising nearly 200 satellites. Serval reduces end-to-end latency for high priority queries from 71.71 hours (incurred by state of the art) to 2 minutes, and 90-th percentile from 149 hours to 47 minutes.