As was astutely noted by Hans, the period of the movement was about 25 days. It turns out that is the time it takes for the sun to rotate once. When I was grabbing the data from JPL Horizons, I listed the target as "coord@10". I should have omitted the "coord", as that means coordinates. Without ...
@PearsonArtPhoto I think that blogging about mistakes you've made on your own web site may be pushing the boundaries of what a proper Stack Exchange answer should be. Should there be some reasonable limit to the number of times this happens?
A space expert seeing such a wild oscillation of a spacecraft's velocity when it was in deep space would likely recognize it as plainly and obviously wrong, and hesitate to post it to the internet.
Something clearly threw off the script. I've improved it since then a bit, and you will actually see that the back to back close approaches are as follows:
Far point from Sun on November 3, 2018 at a distance of 1.668 AU.
Far point from Sun on June 7, 2020 at a distance of 1.663 AU.
I believe...
I'm not suggesting that each time a programmer's oversight ends up as an SE question and answer potentially directs traffic to your money-making site (revenue discussed several times here in this chat). But there may be a perception issue considering that you are also a moderator of the site. Perhaps an "abundance of caution" could be considered in this case?
@uhoh I apologise that I'm not an expert, although by asking and receiving the answer, I now know that in the future this is something I should think about when attempting to solve such problems. Pearson has no control over users going to his site and seeing things that cause them to ask questions. It's the same as any other site posting content related to space exploration, all of them make money, this site just so happens to be owned by a member of our community.
Pearson earning rep and (possibly) money is just a happy side effect of people's willingness to learn and his cooperation in teaching them.
The thing that makes it interesting is the default options actually include coord@, which is something to be aware of. I had no idea, Horizons is a pretty overwhelming site.
I do agree that the question that I asked about data on my site that was wrong doesn't really belong here, and so I've removed that.
From the tutorial:
To select a point on the surface of a target body (limited to those with an IAU rotational model), use this form (units are degrees and km):
{g: E.Long, latitude, h@}BODY [geodetic/planetographic coords]
{c: E.Long, DXY, DZ@}BODY [cylindrical coordinates]
...
@PearsonArtPhoto this answer shows how to do it manually. I hadn't seen any default options for target. This shows a tutorial for origin i.sstatic.net/S6uCg.png Where are the default options for target shown?
Also, I'd put a lot of work answering that question for you. It's fine that you'd accepted your own answer and then later deleted the wrong statements in it, but I felt that my answer contained helpful information
The now invisible and un-viewable answer stated the problem was 7 million kilometers. The diameter of the Sun is 1.4 million. It could not be the "wobble" due to barycentric motion nor could it be what you are saying now.
I mean the now invisible and un-viewable question.
There's a little arrow on the right of everyone else's messages that you can click to get a direct rely. The messages will then link up so the little arrow on the left of the newest message can be used to get back up to the referenced message
@geoffc This is painfully complicated. There are two options. Click the left arrow of your message copy the hyperlink into the message box and delete everything except the last 8 numbers and place a colon in front.
@Edlothiad So the reply to the above would start with :43536853
Or, you can click in the message box, hover over the little arrow and where it shows you were the link will point to (in the bottom left of your browser) copy that after the colon
@uhoh He means, when you click on teh reply button, it pastes a colon, and 8 digit code into your chat box. It does not let you do that to yourself, per se, directly. So his advice is if you look at the hyper link, it contains the needed 8 digits at the end of the link. Ergo, delete the stuff before the last 8 digits....
It is harder for your own messages, sure. It is however easier for anyone wanting to follow the messages back. However for someone else's message. It's much easier than an open ping where you simply type @name as they can see which message you're referencing, and therefore get the context.
It is entirely up to you whether or not you choose to use replies, but the feature exists for a reason, and is useful.
@Edlothiad okay well I will try it here. There is no need to apologize. Indeed you've both acquired a substantial reputation kick from this fortuitous choice of entering the coordinates for a location on the surface of the sun.
Far more than a typical science-based question or thoughtful answer. SE votes can be so fickle sometimes. Congratulations!
The truth is, if that question wasn't asked then I don't know that I would have found the answer, and certainly not as quickly.
I knew there was something off from the plot, but I had attributed the wrong cause to it. It bothered me, but having the question asked, I was provided a comment that gave me the answer.
The person who wrote the comment, however, should have received the bulk of the reputation, not I.
To do this website I've essentially had to learn using Horizons, website design, Plotly.js, some graphic design, and a lot of other things that I've had only a bit of exposure to.
I'm amazed at how well the website has done despite all of that.
The rover has pancam and the wings on it's solar panels that were specifically designed for the MERs (can provide a quote if you want). It also has the rover arm, which holds MB MIMOS II, APXS, MI and RAT.
You can see the little silver wheel on the top, the wheel arrangement, the solar panel wings and pancam.
From the tutorial:
To select a point on the surface of a target body (limited to those with an IAU rotational model), use this form (units are degrees and km):
{g: E.Long, latitude, h@}BODY [geodetic/planetographic coords]
{c: E.Long, DXY, DZ@}BODY [cylindrical coordinates]
...
![We all remember those famous first words spoken by an astronaut on the surface of Mars: "That's one small step fo- HOLY SHIT LOOK OUT IT'S GOT SOME KIND OF DRILL! Get back to the ... [unintelligible] ... [signal lost]"](https://imgs.xkcd.com/comics/opportunity.png "We all remember those famous first words spoken by an astronaut on the surface of Mars: \"That's one small step fo- HOLY SHIT LOOK OUT IT'S GOT SOME KIND OF DRILL! Get back to the ... [unintelligible] ... [signal lost]\"")
