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Title: Automated Science Scheduling for the ECOSTRESS Mission

Paper content:
We describe the use of an automated scheduling system for observation policy design and to schedule operations of the NASA (National Aeronautics and Space Administration) ECOSystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS).
We describe the adaptation of the Compressed Large-scale Activity Scheduler and Planner (CLASP) scheduling system to the ECOSTRESS scheduling problem, highlighting multiple use cases for automated scheduling and several challenges for the scheduling technology: handling long-term campaigns with changing information, Mass Storage Unit Ring Buffer operations challenges, and orbit uncertainty.
The described scheduling system has been used for operations of the ECOSTRESS instrument since its nominal operations start July 2018 and is expected to operate until mission end in Summer 2019.
NASA's ECOSTRESS mission (NASA 2019) seeks to better understand how much water plants need and how they respond to stress.
Two processes show how plants use water: transpiration and evaporation.
Transpiration is the process of plants losing water through tiny pores in their leaves.
Evaporation of water from the soil surrounding plants affects how much water the plants can use.
ECOSTRESS measures the temperature of plants to understand combined evaporation and transpiration, known as evapotranspiration.ECOSTRESS launched on June 29, 2018 to the ISS (International Space Station) on a Space-X Falcon 9 rocket as part of a resupply mission.
The instrument is attached to the Japanese Experiment Module Exposed Facility (JEM-EF) on the ISS and targets key biomes on the Earth's surface, as well as calibration/validation sites.
Other science targets include cities and volcanoes.
From the orbit of the Space Station FIG1 ), the instrument can see target regions at varying times throughout the day, rather than at a fixed time of day, allowing scientists to understand plant water use throughout the day.The instrument used for ECOSTRESS is a thermal infrared radiometer.
A double-sided scan mirror, rotating at a constant 25.4 rpm, allows the telescope to view a 53°-wide nadir cross-track swath with one scan per 1.18 seconds.
The nominal observation unit is a scene, made up of 44 scans, and takes roughly 52 seconds to acquire.
For simplification of operations, we consider that ECOSTRESS scenes are 52 seconds long.
About 1000 scenes may be acquired in a given week.
FIG2 shows a set of planned observations over North America.
Each square represents one 52-second long scene.CLASP BID4 was initially used prelaunch as a tool to analyze the addition of a new science campaign.
CLASP was then used for operations to generate command sequences for the instrument.
The command sequences are translated from the observation schedule generated by CLASP, and include other time and location dependent instrument actions besides observations, such as hardware power cycles through high radiation environments.
Each mission comes with its own set of challenges, and there were three specifically that required adaptations to CLASP as follows.•
ECOSTRESS has a long-term science campaign that we need to satisfy. From
week to week, the orbital ephemeris can change, and thus the schedule needs to be updated each week. We need
to be able to account for previously executed observations when scheduling for the future.• An issue
with the instrument Mass Storage Unit (MSU) was discovered, and rather than performing an instrument firmware update, we proposed a ground-based solution that accounts for this additional complexity in the data modeling in the schedule.• The uncertainty
in the orbital ephemeris (predictions of In the remainder of this paper, we describe these operational challenges and how we addressed them successfully. We also validate
our methods used through computational analysis.
This paper has described the use of an automated scheduling system in the analysis and operations for the ECOSTRESS mission.
Changing orbital ephemeris and long-term campaign goals required adapting CLASP to consider past observations in scheduling for the future.
The issue with the instrument ring buffer required scheduling with additional constraints, as well as scheduling another type of instrument activity.
The uncertainty of the ISS orbital position required adapting how observations are scheduled.
Through computational analysis we showed that our method for addressing the ring buffer approached the performance of schedules produced that did not have the added constraints, and that the second method of building observations up rather outperformed the method of adding a fixed amount of observational time to ensure no regions of interest were missed.

assistant: text: This paper presents an adaptation of an automated scheduling system, CLASP, to target an EO experiment (ECOSTRESS) on the ISS.