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<text>
 <s id="1">
    <w id="1.1">Notes</w>
</s>
 <s id="2">
    <w id="2.1">↑</w>
    <w id="2.2">All</w>
    <w id="2.3">astronomical</w>
    <w id="2.4">quantities</w>
    <w id="2.5">vary</w>
    <w id="2.6">,</w>
    <w id="2.7">both</w>
    <w id="2.8">secularly</w>
    <w id="2.9">and</w>
    <w id="2.10">periodically</w>
    <w id="2.11">.</w>
</s>
 <s id="3">
    <w id="3.1">The</w>
    <w id="3.2">quantities</w>
    <w id="3.3">given</w>
    <w id="3.4">are</w>
    <w id="3.5">the</w>
    <w id="3.6">values</w>
    <w id="3.7">at</w>
    <w id="3.8">the</w>
    <w id="3.9">instant</w>
    <w id="3.10">J2000.0</w>
    <w id="3.11">of</w>
    <w id="3.12">the</w>
    <w id="3.13">secular</w>
    <w id="3.14">variation</w>
    <w id="3.15">,</w>
    <w id="3.16">ignoring</w>
    <w id="3.17">all</w>
    <w id="3.18">periodic</w>
    <w id="3.19">variations</w>
    <w id="3.20">.</w>
</s>
 <s id="4">
    <w id="4.1">1</w>
    <w id="4.2">2</w>
    <w id="4.3">aphelion</w>
    <w id="4.4">=</w>
    <w id="4.5">a</w>
    <w id="4.6">×</w>
    <w id="4.7">(</w>
    <w id="4.8">1</w>
    <w id="4.9">+</w>
    <w id="4.10">e</w>
    <w id="4.11">)</w>
    <w id="4.12">;</w>
    <w id="4.13">perihelion</w>
    <w id="4.14">=</w>
    <w id="4.15">a</w>
    <w id="4.16">×</w>
    <w id="4.17">(</w>
    <w id="4.18">1</w>
    <w id="4.19">–</w>
    <w id="4.20">e</w>
    <w id="4.21">)</w>
    <w id="4.22">,</w>
    <w id="4.23">where</w>
    <w id="4.24">a</w>
    <w id="4.25">is</w>
    <w id="4.26">the</w>
    <w id="4.27">semi-major</w>
    <w id="4.28">axis</w>
    <w id="4.29">and</w>
    <w id="4.30">e</w>
    <w id="4.31">is</w>
    <w id="4.32">the</w>
    <w id="4.33">eccentricity</w>
    <w id="4.34">.</w>
</s>
 <s id="5">
    <w id="5.1">The</w>
    <w id="5.2">difference</w>
    <w id="5.3">between</w>
    <w id="5.4">Earth</w>
    <w id="5.5">'s</w>
    <w id="5.6">perihelion</w>
    <w id="5.7">and</w>
    <w id="5.8">aphelion</w>
    <w id="5.9">is</w>
    <w id="5.10">5</w>
    <w id="5.11">million</w>
    <w id="5.12">kilometers</w>
    <w id="5.13">.</w>
    <w id="5.14">↑</w>
    <w id="5.15">United</w>
    <w id="5.16">States</w>
    <w id="5.17">Strategic</w>
    <w id="5.18">Command</w>
    <w id="5.19">tracks</w>
    <w id="5.20">about</w>
    <w id="5.21">15,000</w>
    <w id="5.22">other</w>
    <w id="5.23">artificial</w>