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a. I hope this is the case, but if it is, it would seem to be a huge oversight on STK's part; I'll take your word for it. There For it to be off that much in the gif seems wrong. To note, there is a distinction made here in STK (Satellites - Propagators - Two-Body, J2 Perturbation & J4 Perturbation (agi.com)):
- J2Perturbation includes the point mass effect as well as the dominant effect of the asymmetry in the gravitational field (i.e. the J2 term in the gravity field, representing North/South hemisphere oblateness); J4 additionally considers the next most important oblateness effects (i.e., the J2^2 and J4 terms in addition to J2). None of these propagators model atmospheric drag, solar radiation pressure or third body gravity; they only account for a few terms of a full gravity field model.
- These propagators are often used in early studies (where vehicle data is usually unavailable for producing more accurate ephemeris) to perform trending analysis: J2 Perturbation is often used for short analyses (weeks) and J4Perturbation often for long analyses (months, years).
Even thenwhen i implemented this, it doesn't look like it makes much of a difference when I simulate it with J4.
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