I am in love with the images available at https://epic.gsfc.nasa.gov/ taken from the DSCOVR satellite. I am curious though as to why some dates are unavailable to select.

The calendar date picker tool has dates that are unavailable to select. For example 2019 February on the 5th and 19th.

Is it because no images were taken on those dates, or none scheduled, or is there some other reason why they wouldn't be available?

DSCOVR EPIC February 2019 image availability

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    $\begingroup$ I noticed that the dates are about 2 weeks apart. I suspect this is some kind of a cycle, maybe the sun is reflecting particularly strong on those days and it makes the image harder to read? Hard to say... $\endgroup$ – PearsonArtPhoto Apr 19 at 12:39
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    $\begingroup$ @PearsonArtPhoto at Sun-Earth L1 the Lissajous orbital period is roughly five or six months. If the Moon somehow interfered, it would be roughly four weeks between passes, not two. I can't imagine a source of a two-week cycle. Maybe there were scheduling conflicts at the ground station, or Staff meetings on Mondays that ran late? $\endgroup$ – uhoh Apr 19 at 13:58
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    $\begingroup$ Thanks for the input, as far as the dates being a cycle of some sort there are various others that don't seem to match any pattern, occasionally there are multiple days in a row also, they seem to be sporadic. Could it be some kind of solar interference with the electronics maybe? $\endgroup$ – Mike Apr 19 at 14:25
  • $\begingroup$ It's because pictures with UFO fly-by are classified ;) $\endgroup$ – Hagen von Eitzen Apr 20 at 9:54
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    $\begingroup$ @uhoh it's not lunar interference, they actually love that. see the link in my answer. $\endgroup$ – DuffBeerBaron Apr 24 at 15:07

I can't say for sure, I but would guess that it's due to maneuvers. There are other satellites in Libration Point Orbits that maneuver on the 2-3 week time frame. (They do so no matter what, it's not on an as-needed basis) Also there are a couple of factors associated with maneuvers that can preclude the ability to 'do science' on the spacecraft:

  • The spacecraft may have to slew to a different attitude for the maneuver that would point the camera away from the Earth.
  • The maneuver itself may cause too much jitter for the camera to take a clear picture.
  • There could be exhaust plumes associated with the thruster firings that might blur the imagery.

Most likely it's just the first one, but these are all things I've heard bandied about with regard to other satellites.

For the irregular outages, those could be other satellite maintenance issues, such as momentum unloads, or as you speculated scheduling conflicts, or even hardware issues.

It's not lunar interference, they take images throughout any transits:



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