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| 1 | + |
1 | 2 | This research aims to expand the algorithmic capability for tasking sensors to investigate human-specified hypotheses about space objects (SOs).
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2 | 3 | The goal is to improve the ability to evaluate internal- and physical- state hypotheses in cases where there are many objects and a collection of sensors with diverse capabilities.
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| -**Problem Description** |
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| -Describe the problem of catalog maintenance and hypothesis resolution |
| 6 | +<!-- **Problem Description** --> |
| 7 | +<!-- Describe the problem of catalog maintenance and hypothesis resolution --> |
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8 | 9 |
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9 | 10 | **Technical Approach**
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| -Describe our technical approach: |
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| -1. Generating a base plan using ILP |
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| -2. Plan only over the OOI, where an action is a change in the plan |
| 11 | +The approach can be broken down into two main steps: |
| 12 | +1. Generating a base plan using integer linear programming |
| 13 | +2. Generating a refined MCTS plan accounting for the object of interest |
| 14 | + |
| 15 | + |
| 16 | +### 1) Integer Linear Program |
| 17 | +The base integer linear programming approach aims to judiciously allocate sensors to space objects in a manner where the severity of the worst-case scenario is minimized. |
| 18 | + |
| 19 | +Formally, the ILP is given by |
| 20 | +<script type="text/javascript" src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-mml-chtml.js"></script> |
| 21 | +$$ |
| 22 | +\begin{aligned} |
| 23 | +\text{maximize} \quad & t \\ |
| 24 | +\text{subject to} \quad & X_{ijt} \in \{0,1\}^{I\times J \times T} \\ |
| 25 | +& X_{ijt} \preceq O \\ |
| 26 | +& t \preceq \sum_{j,t} X_{ijt} \\ |
| 27 | +& \sum_{i} X_{ijt} \preceq 1 \, . |
| 28 | +\end{aligned} |
| 29 | +$$ |
| 30 | + |
| 31 | +Here $$X_{ijt}$$ is a binary 3-dimensional control variable representing whether or not observer $$j$$ observers object $$i$$ at time step $$t$$, and $$O_{ijt}$$ represents whether or not observer $$j$$ *is able to* observe object $$i$$ at time $$t$$. |
| 32 | + |
| 33 | +For ground based-sensors, the ILP plan can be visualized as follows: |
| 34 | + |
| 35 | +. |
13 | 36 |
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| 37 | +### 2) Monte Carlo Tree Search |
| 38 | +Building on the ILP solution as a baseline, we assume the existence of an object of interest in the catalogue, for which we seek to resolve a specific hypothesis. This work focuses on determining the drag configuration for the object in question. To achieve this, we use Monte Carlo Tree Search (MCTS) applied to a belief Markov Decision Process (MDP). The goal of the MCTS solver is to minimize the entropy of the distribution over possible hypotheses while minimally disrupting the baseline catalogue maintenance plan. |
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