DSCOVR Options

[hendric]

I found a reference that DSCOVR's L1 orbit varies the Sun-Earth-DSCOVR angle by 4-15*. I assume like Soho the ellipse is mostly East/West. September's eclipse is a partial in the southern hemisphere. I expect it will be difficult to notice since it will be over mostly dark water, far from the subsolar point. The March 8th total solar eclipse next year should be very noticeably, since it will cross the central Pacific. Since the umbra will stay on Earth's surface for over 3 hours, I think we should get a couple of pics of it.

http://www.timeanddate.com/eclipse/list.html

[JRehling]

The difference between Earth-Moon albedo can also be seen in person when a gibbous Moon rises in the afternoon or sets in the morning and can be compared to distant hills, clouds, etc. on Earth, although there are many factors that can ruin the comparison.

[scalbers]

The gibbous moon is an interesting comparison. The land surface of the Earth can be relatively close to the lunar albedo, compared with the clouds. When looking at specific locations relative to the sun, we can consider the reflectance since the albedo is more of an averaged quantity. At some point I may test my rendering software to show the DSCOVR view with the moon included.

[Explorer1]

No news on the proposed daily 'pipeline'? There haven't been any images released in September at all (not trying to sounding ungrateful, just wondering about what the holdup is!)

[ZLD]

Just noticed the DSCOVR website had a news update yesterday. More or less it talks about the camera on board and mentions that a new website was created to host the available data.

http://epic.gsfc.nasa.gov/

Doesn't seem to be able to finish loading for me at this moment in time however.

[dvandorn]

It took me three tries to load the website yesterday, but when it finally loaded I found that I could pull up whole-Earth images from two days prior -- which happened to be my 60th birthday. It lets you scroll through images taken a few hours apart throughout a given day.

I was able to capture the image of the western hemisphere, featuring my home continent, as it appeared in the middle of my birthday. Kewl! I now have it as my desktop.

-the other Doug

[ZLD]

Yeah, it finally loaded for me as well. Probably took 10m to load the page. Either they are getting pounded with site hits or they dug up a clunker from the basement to host the site.

[Explorer1]

At least! Very nice, and apparently archives going back a few months. Nice to see things like the distance information and angle from the sun too.
Eventually the Moon will pass behind/in front of our blue marble again....

[Astroboy]

The timing of the pictures seems really random, and the Moon transit sequence isn't included. Are we only going to get handfuls of images for the time being?

[scalbers]

Does the moon always transit as seen from DSCOVR? There's enough deviation of DSCOVR from the Sun - Earth line, and the moon's orbital inclination effect that could cause a miss.

The timing of the pictures seems to be every 2 hours or a bit less. Maybe some days they aren't downlinking as many.

The website has an email contact that may help with some of our questions.

[Explorer1]

I think they mentioned in the first press release on the lunar transit that it doesn't happened very often (think of eclipse frequencies). All three (Earth, Moon, DSCOVR) have to be on the same plane, so it's about twice a year.
None of the images show the Moon setting behind the Earth either, however; it might be a matter of timing the image to get the Moon in frame before and after it passes behind Earth's disc....

[elakdawalla]

I don't have direct answers to the questions being asked here, but I do have a little information that might be useful to people. When they first launched the website, I sent this inquiry to the media contact:

I'm enjoying browsing the new DSCOVR EPIC website; it's a beautiful camera. I am wondering if there is a place where I can view a table or text file or something that contains basic metadata for the images (primarily a list of links to images with their timestamps). The reason I ask is because I'm interested in trying to make animations of Earth over time from a fixed longitude, but the way the website is set up, it's laborious to identify which days contain images taken at roughly the same times. Such a table would also allow people to invent different ways of displaying/searching the data.

My inquiry was forwarded to Adam Szabo, who replied:

EPIC Daily "Blue Marble" API
The API URL is:
http://epic.gsfc.nasa.gov/api/images.php

This gets you a list of the latest day's images & metadata.

OR

http://epic.gsfc.nasa.gov/api/images.php?d...amp;w=X&e=Y

The second form's optional parameters allow you to focus in to geographical regions that were in view (technically, longitudinal bounding points) on a given date.

For instance: Using North America's boundaries of east = -53.034, and west = -170.859 and choosing August 24, 2015, the URL would look like this:

http://epic.gsfc.nasa.gov/api/images.php?d...9&e=-53.034

The date parameter is unpadded(e.g. 2015-9-1, vs. 2015-09-01 for September 1, 2015), and optional. Leaving the date off will default to the latest image set.

Leaving out the coordinates gets you every image for whatever date is returned.
Adding either longitudinal parameter returns all images for the given date, for which the supplied longitude is in view of the camera.


The JSON data looks like this:

ImageData object:

{
"image": "epic_1b_20150826231708_00", // image name sans extension.
"caption": "About an image", // Will contain a caption
"coords": "{}", // Contains a JSON string representing a Coordinates object.
"date": "2015-08-26 23:17:08" // The date the capture sequence for the image was initiated
}

ImageData notes:

For the image field to be useful, it has to be added to a URL. Image URLs differ depending upon purpose.

Given an image name of "epic_1b_20150901205648_00" (taken Sept 1, 2015, with the camera aimed
at 3 typhoons in the pacific (my favorite)), we have:

For compressed JPG thumbnails, the path would be

http://epic.gsfc.nasa.gov/epic-archive/thu...01205648_00.jpg

For full-size, compressed JPG previews, the path would be

http://epic.gsfc.nasa.gov/epic-archive/jpg...01205648_00.jpg

For full-size original PNG images, the path would

http://epic.gsfc.nasa.gov/epic-archive/png...01205648_00.png


Coordinates object

{
"centroid_coordinates": { // Geographical coordinates that the satellite is looking at
"lat": 4.076132,
"lon": -169.648562
},
"dscovr_j2000_position": { // Position of the satellite in space
"x": -1439710.750000,
"y": 659227.437500,
"z": 113316.414062
},
"lunar_j2000_position": { // Position of the moon in space
"x": 153199.062500,
"y": -319797.531250,
"z": -104905.093750
},
"sun_j2000_position": { // Position of the sun in space
"x": -134918656.000000,
"y": 62555808.000000,
"z": 27119770.000000
},
"attitude_quaternions": { // Satellite attitude
"q0": 0.976360,
"q1": -0.212080,
"q2": -0.039540,
"q3": 0.013750
}
}

[Explorer1]

The seasons are changing; yesterdays image (November 27th at 12:00 GMT) is giving a sense of deja vu....
http://epic.gsfc.nasa.gov/epic-archive/png...26081200_00.png

A little over a week until the anniversary of the Blue Marble that started it all.

[Explorer1]

Apparently the lunar eclipse images were saved for AGU 2015, so they weren't on the website (makes sense; the craft had to track the Moon, not Earth, so it would have been a confusing sequence).
http://www.bbc.com/news/science-environment-35076402

[scalbers]

Yes, this was shown yesterday here at AGU in a panel discussion including Al Gore, Adam Szabo and several additional science team members. It was suggested by the panel that the images from DSCOVR would look much nicer with some motion interpolation applied to make a continuous movie. Sounds right up UMSF's alley

Also being discussed are followup missions with improved cameras.