# What decides which flybys show an anomaly? · Earth flyby anomaly > Five answers have been proposed. None is ahead on the evidence yet. Five are still possible. Source: https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE9G65APR/what-decides-which-flybys-show-an-anomaly Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-26T11:57:26+00:00 --- **0** # What decides which flybys show an anomaly? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·Part of [What produces the velocity changes seen in some Earth flybys?](https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE98C43P6/what-produces-the-velocity-changes-seen-in-some-earth-flybys)·5 answers·0·0 following **Five answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Five answers have been proposed. None is ahead on the evidence yet. Five are still possible. ## Why it matters Any explanation must account for both the anomalies and the nulls; the empirical formulas proposed so far have not predicted new flybys⁠[[1]](https://mysteriesdept.com/sources/SRC0CWYE16J6YDA/the-flyby-anomaly-a-multivariate-analysis-approach). ## Answers 5 [**An alternative empirical formula (Busack 2007) that predicted the Rosetta null results.** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYEE4M3ZDD/an-alternative-empirical-formula-busack-2007-that-predicted) Tested, but the results don't decide it Evidence: 1 against Disputed [**Local parameters at perigee, as for a latitude-dependent force of about 300 km range.** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYEEM83BZ2/local-parameters-at-perigee-as-for-a-latitude-dependent) Not tested enough to call either way Evidence: 1 for Still possible [**None of these.** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYEFKG5G5G/none-of-these) Not tested enough to call either way Evidence: none yet Still possible [**The difference between incoming and outgoing declinations, as in the Anderson formula.** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYEDD65GBF/the-difference-between-incoming-and-outgoing-declinations-as) Failed a test; not refuted outright Evidence: 1 for, 1 against Disputed [**The land-sea distribution under the trajectory modulates the effect.** ](https://mysteriesdept.com/mysteries/flyby-anomaly/answers/ANS0CWYEF3W12JE/the-land-sea-distribution-under-the-trajectory-modulates-the) Not tested enough to call either way Evidence: 1 for Still possible ## History 1. 2008[Anderson et al. puts forward: the difference between incoming and outgoing declinations, as in the Anderson formula.](https://mysteriesdept.com/sources/SRC0CWYDZQP6RHF/anomalous-orbital-energy-changes-observed-during-spacecraft) 1. 2008[Anderson et al.: fits the six flybys known in 2008.](https://mysteriesdept.com/sources/SRC0CWYDZQP6RHF/anomalous-orbital-energy-changes-observed-during-spacecraft)For: The difference between incoming and outgoing declinations, as in the Anderson formula. 1. 2013[Busack puts forward: an alternative empirical formula (Busack 2007) that predicted the Rosetta null results.](https://mysteriesdept.com/sources/SRC0CWYE0YR11F9/expected-velocity-anomaly-for-the-earth-flyby-of-juno) 1. 2017[Acedo puts forward: local parameters at perigee, as for a latitude-dependent force of about 300 km range.](https://mysteriesdept.com/sources/SRC0CWYE16J6YDA/the-flyby-anomaly-a-multivariate-analysis-approach) 1. 2017[Acedo: a multivariate fit of nine flybys predicts non-zero values only for Galileo II, NEAR and Cassini within…](https://mysteriesdept.com/sources/SRC0CWYE16J6YDA/the-flyby-anomaly-a-multivariate-analysis-approach)For: Local parameters at perigee, as for a latitude-dependent force of about 300 km range. 1. 2018[Acedo et al.: juno showed no clear anomaly against a predicted +6 mm/s.](https://mysteriesdept.com/sources/SRC0CWYE1EC5ADC/a-possible-flyby-anomaly-for-juno-at-jupiter)Against: The difference between incoming and outgoing declinations, as in the Anderson formula. 1. 2018[Acedo et al.: juno's anomaly was at the threshold of detection or absent.](https://mysteriesdept.com/sources/SRC0CWYE1EC5ADC/a-possible-flyby-anomaly-for-juno-at-jupiter)Against: An alternative empirical formula (Busack 2007) that predicted the Rosetta null results. 1. 2026[Yalcinbas puts forward: the land-sea distribution under the trajectory modulates the effect.](https://mysteriesdept.com/sources/SRC0CWYE3WG0ZVE/a-sign-stable-earth-fixed-modulation-in-earth-flyby) 1. 2026[Yalcinbas: a stable sign structure across the primary flyby set under changes of weighting.](https://mysteriesdept.com/sources/SRC0CWYE3WG0ZVE/a-sign-stable-earth-fixed-modulation-in-earth-flyby)For: The land-sea distribution under the trajectory modulates the effect. 1. 26 Oct 2026Asked on this site ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE9G65APR/what-decides-which-flybys-show-an-anomaly%23discussion) Help with this question [ **Propose an answer** Something the evidence could support or rule out ] [ **Propose an answer** Something the evidence could support or rule out ](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE9G65APR/what-decides-which-flybys-show-an-anomaly%23add-answer) [ **Add evidence** A result for or against an answer ] [ **Add evidence** A result for or against an answer ](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE9G65APR/what-decides-which-flybys-show-an-anomaly%23add-evidence) [ **Ask a sub-question** A smaller question that would help settle this one ] [ **Ask a sub-question** A smaller question that would help settle this one ](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE9G65APR/what-decides-which-flybys-show-an-anomaly%23add-question) [ **Add a source** A paper, archive record or image ] [ **Add a source** A paper, archive record or image ](https://mysteriesdept.com/signin?next=/mysteries/flyby-anomaly/questions/QST0CWYE9G65APR/what-decides-which-flybys-show-an-anomaly%23add-source) Where it fits Earth flyby anomaly [**What produces the velocity changes seen in some Earth flybys?** ](https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE98C43P6/what-produces-the-velocity-changes-seen-in-some-earth-flybys)Key question · most likely an error or inconsistency in trajectory modelling and navigation software (reference frames, spheres of… [Does the anomaly occur at other planets?](https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE9ZT1W27/does-the-anomaly-occur-at-other-planets)Open · 3 answers, inconclusive [If the anomaly is real new physics, what kind?](https://mysteriesdept.com/mysteries/flyby-anomaly/questions/QST0CWYE9R02K3H/if-the-anomaly-is-real-new-physics-what-kind)Open · 4 answers, inconclusive **What decides which flybys show an anomaly?** You're here · 5 answers, inconclusive [ Ask a question under this one ]