19 Sep 2022
19 Sep 2022
Status: a revised version of this preprint was accepted for the journal AMT.

Earth Observations from the Moon surface: dependence on lunar libration

Nick Gorkavyi1, Nickolay Krotkov2, and Alexander Marshak2 Nick Gorkavyi et al.
  • 1Science Systems and Applications, Inc., Lanham, MD, USA
  • 2National Aeronautics and Space Administration (NASA), Goddard Space Flight Center (GSFC), Greenbelt, MD, USA

Abstract. Observing the Earth from the Moon has important scientific advantages. The angular diameter of the Earth as seen from the Moon surface is 1.9° ± 0.1°(the angular size varies due to the change in the distance between the Earth and the Moon). The libration of the Moon in latitude reaches an amplitude of 6.68° and has a main period of 27.21 days (or 653.1 hours). The libration of the Moon in longitude, reaching 7.9°, has a period of 27.55 days (or 661.3 hours). This causes the center of the Earth move in the Moon’s sky in a rectangle measuring 13.4°× 15.8°. The trajectory of the Earth's motion in this rectangle changes its shape with a period of 6 years. This apparent librational movement of the Earth in the Moon’s sky complicates observations of the Earth. The paper proposes to turn this disadvantage into an advantage and place a multi-slit spectrometer on the Moon surface on a fixed platform. The libration motion and the daily rotation of the Earth will act as a natural replacement for the scanning mechanism.

Nick Gorkavyi et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2022-158', Anonymous Referee #1, 10 Oct 2022
  • RC2: 'Comment on amt-2022-158', Liviu Ivanescu, 19 Oct 2022

Nick Gorkavyi et al.

Nick Gorkavyi et al.


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Short summary
The article discusses topical issues of the visible (libration) motion of the Earth in the sky of the Moon in a rectangle measuring 13.4°× 15.8°. On the one hand, the librations of the Moon make these observations difficult, and on the other hand, they can be used as a natural scanning mechanism for cameras and spectroscopes mounted on a fixed platform on the surface of the Moon.