jessriedel 4 days ago

My personal favorite astronomical image of all time is this view taken by New Horizon during its retreat from Pluto:

It shows atmospheric haze and the curvature of the planet in the same picture as stark terrain features. (It's a real image; not a reconstructed 3D visualization.) The Hillary Montes break into the limb (skyline) near the top of the image.

  • yig 4 days ago

    Any idea why it appears black and white? The links say it was taken with the "Multispectral Visual Imaging Camera (MVIC)", whose description suggests it can capture in visible spectra. Is Pluto really made of grey?

    • avian 4 days ago

      Very likely the image was taken using only one MVIC filter (it has seven according to Wikipedia) [1] and is hence monochromatic.

      Since this is near sunset and hence very dark, maybe they chose one of the panchromatic filters to admit as much light to the detector as possible.

      Another possibility is that researchers didn't think there was any scientific value in capturing the image through multiple filters and rather saved the limited on-board memory for some other data.


      • dr_zoidberg 4 days ago

        It's a composite of LORRI images, which is panchromatic. That means it doesn't have any filters in between, and it measures the intensity of light across all visible wavelengths (and probably a bit of near IR -- so panchromatic), that's why it's grayscale -- it's measuring the intensity of light.

        I've downloaded all the mission LORRI and MVIC raw files, and I know "by eye" that MVIC isn't near as good resolution as LORRI.

        Edit: after checking the linked file, then yes, this version must be an upscaled MVIC image (I saw an almost 7k by 3k image and immediately thought of LORRI). Yet, there are same views from the LORRI instrument, which are far more detailed.

        • jessriedel 3 days ago

          Are you saying there is a version of this photo at even higher resolution? Is there anything you could tell me that would help me track it down? It's sort of a hard thing to Google for, and hunting through the raw NASA database seems like a needle in a haystack.

          EDIT: Based on this, I think you might have just gotten the two cameras confused :)

          > LORRI is a simple camera to understand -- it's point and shoot. It is black-and-white, with a square detector, 1024 pixels square, over an extremely narrow field of view of 0.29 degrees....Sometimes, to keep file sizes small and improve signal in low light situations, you can bin LORRI images 4x4, so the resulting pictures are 256 pixels square. That's pretty much it for LORRI....

          > MVIC is quite different from LORRI...The detector is 5024 pixels wide, of which 5000 are actually photoactive, so its images are 5000 pixels wide by an arbitrary number of pixels long.

          • dr_zoidberg 2 days ago

            Didn't confuse them, LORRI is basically a camera at the end of a long telescope, hence it gives higher resolution images.

            But yeah, going over the files at the time this MVIC image was generated, LORRI took a few (very) close up images but it doesn't have any one having such a large field of view (since MVIC is not as magnified, then it's able to take such widefield images).

            Edit: And after a lot of searching, I found the image: nh-p-mvic-3-pluto-v3.0/data/20150714_029918/

            By the way, I'm glad you threw me into this search. Having found this specific image gave me a few good ideas to work over them again, with new things I've learned since the last times I visited them.

    • jessriedel 3 days ago

      I've now found the answer:

      > Question: If MVIC is New Horizons' color camera, why is this image black-and-white?

      > Answer: Either because only one channel was used to take this image, or because they have only received one channel's worth of data on the ground. To make a single color image, you have to downlink three photos, one each from three different channels; in other words, color images take three times as much data as black-and-white ones. As a matter of fact, New Horizons team member John Spencer has confirmed that only the panchromatic channel was used for this photo, because of the limited time and demands on the spacecraft during closest approach. If they were shooting in color, they wouldn't also be able to do as much with LORRI at the same time.

    • jessriedel 4 days ago

      I don't know why. My best guess is that it's low lighting, and there isn't much color information available. I think I've seen a colorized version somewhere, but can't remember if the colors were authentic. Very interested if someone could track that down.

  • droithomme 4 days ago

    Thanks, I had not seen that image before. It's amazing that Pluto has an atmosphere. Was this suspected before the New Horizon's mission? I seem to recall it once being presented as considered a cold rock with no interesting features or possible atmosphere.

    • yaks_hairbrush 4 days ago

      It was indeed established that Pluto had an atmosphere before the New Horizon flyby. The atmosphere is mostly seasonal. The air freezes when Pluto is far from the sun, and sublimates again when it's near.

      • lmkg 4 days ago

        Thank you for reminding me how strange the universe can be sometimes.

droithomme 4 days ago

Interesting about the 1000 ft tall ice shards. The article mentions a possible orbiter mission to Pluto. Is it even possible? The spacecraft would have to either massively decelerate at the end of the mission, meaning take a huge amount of fuel with itself, or would have to travel much slower, with the mission possibly taking decades to arrive.

In 2017 some astrophysicists met to discuss a possible orbiter mission:

They've also discussed a Charon lander, but seem to be now preferring an orbiter with a complex dual-object orbit.

In 2017 they decided to firm up the plan so they can make a formal proposal at a 2020 meeting where NASA decides what it wants to do over the next decade. So we likely will hear a lot about how this would work next year.

  • drjesusphd 4 days ago

    "Travelling much slower" isn't really an option either. By the time a craft encounters Pluto, the problem is that it's going too slow. It then has to match the (higher) orbital speed, and Pluto's gravity is not helping much.

    • droithomme 4 days ago

      You bring up a good point regarding the relative speeds.

      Pluto on average travels 4.7 km/sec or 16,800 km/hr.

      New Horizons, on a 9 yr mission to arrive, was traveling 50,700 km/hr as it passed Pluto. So it was going much faster than Pluto, however it was passing almost orthogonal to Pluto's trajectory.

      It seems an orbiter would want to arrive using some complex slingshot mission around various solar system objects, and taking a catch up trajectory that approaches Pluto more tangentially to its orbit rather than orthogonally.

      That seems more doable than when I first balked at this. Since gravity assist/slingshots can be used to slow down as well as speed up perhaps it zooms out there fast, then slingshots to nearly meet the speed and direction of Pluto, meeting up with it at its orbital path sideways and only needing a small correction at the end to insert itself into orbit.

      • T-hawk 4 days ago

        Matching speeds to the target object isn't all that difficult, right. The problem is the travel time becomes enormous to a distant target object, because it's going so slow comparatively.

        Pluto's orbital period is 248 years. If you aim to match its velocity when you arrive, the journey takes a significant fraction of those 248 years. Compare Mars, where the orbital period is 22 months, and a Hohmann transfer orbit takes 9. A similar trajectory to Pluto would be on the order of 80 to 90 years.

        It's not just about the magnitude of the speed vector, it's also the direction. To match and orbit Pluto, you need that 4.7 km/sec to be tangent to the sun. You need to start out slow enough so that your radial velocity can fall to zero by the time you get there. You can't apply more radial velocity to get there faster, either by launch or slingshot, if there isn't equivalent fuel or mass to decelerate you; you'll overshoot as New Horizons did.

        • burfog 4 days ago

          We now have ion thrusters, which are great for when you need a huge velocity change but can take your sweet time to do it.

  • avian 4 days ago

    > The article mentions a possible orbiter mission to Pluto. Is it even possible?

    I can't read the article about the orbiter mission, but a lander concept was proposed in 2017. Their idea was to use aerobreaking with a giant inflatable balloon, using New Horizon data on atmosphere density as a guideline for the maneuver:

crocal 4 days ago

Anyone else would like to join a trek from Balrog to Cthulhu on a frosty Plutonian summer day?

  • Ididntdothis 4 days ago

    You could take a nice swim in a nitrogen lake :)

Ididntdothis 4 days ago

Does anyone know what shutter speeds and ISO they are using for such pictures? It must be dark out there. Or do concepts like shutter speed and ISO not make sense for the type of camera they are using?

  • dr_zoidberg 4 days ago

    Shutter speed yes, ISO... I think you can check the gain of the sensor used for an image, which is a similar concept. You can see this information on the FITS files ("the raws") metadata.

api 4 days ago

I love that there is a Cthulhu region, especially given that Pluto is Yuggoth. :)