Satellite Orbit Tracker: implement most-current SGP models and algorithms in JavaScript, then use to visualize hundreds of satellites with any browser
License: BSD 3-Clause "New" or "Revised" License
If I add a second BilboardCollection to contain the Geo location marker, the satellite picker can't pick any of the satellites that lie within the disk of the Earth globe. It can pick satelites outside the disk, in the atmosphere. This behaves the same if you zoom or rotate: inside disk fails, outside succeeds.
If we comment out the call which creates the Geo marker billboard collection, we can pick inside and outside the Earth's disk.
Perhaps this is something fixed in a new version of Cesium? There's a discussion about multiple BillboardCollections and picking
science.nasa.gov/missions/? or NSSDC or both
Would be cool to pull it in but maybe we don't want i-frames? do we want to proxy it?
Found an not-yet-implemented function call likely threw off calculations.
See dpper.js for example:
if (typeof(opsmode) === 'undefined') {
throw new Error("Global opsmode is undefined, must be 'a' or 'i'");
}
if ((opsmode !== 'a') && (opsmode !== 'i')) {
throw new Error("Global must be 'a' or 'i' but opsmode=" + opsmode);
}
Is X along "bottom" with Y increasing as you go "up" like textbook coordinates?
Or is X along top with Y increadsing as you go down the page, like some screen coordinate systems?
"it's just javascript" so we can add an attribute
x, y, z and latitude are OK.
Comparing with www.isstracker.com
Lots of satellites seem to have the same calculated height and velocity, which seems unlikely.
This worked, but complicated testing so I'm just reading the TLE data from the <textarea>
Restore the functionality of the file browser so it will work like the MATLAB version.
Orbit now looks like Heavens above, more or less.
Don't know what this came from; perhaps will go away if we use char-array per other ticket?
Uncaught TypeError: Cannot read property 'length' of undefined twoline2rv.js:131
setCharAt twoline2rv.js:131
twoline2rv twoline2rv.js:158
testmat testmat.js:199
(anonymous function) testmat_test.js:
72 comes from whichconst, should this be passed as global? Or should we get the set of vars returned by getgravc() as globals from caller and test invocation?
Regardless how we un-hard-wire this, we should have tests to ensure we're getting real values for those.
Some functions like dpper(...) modify their input variables. This means we can't make assertions that output these values. We have to save the original values when the function's invoked, then emit them in our assert() generation.
This is easy to miss
NB: dpper take 39 input parameters, all floats except one string. Strings and arrays are treated as scalar numerics with silent failures on conversion.
Be sure to set EXTRACT_ALL = YES to get auto-generated documentation for code without comments. There are other parameters for generating call trees and such, not sure if they work with the converted MatLab code.
http://gnu-octave.blogspot.com/2007/10/doxygen-for-octave.html
Display them for the correct satellite.
Use a generic icon for all others.
We may need to make shiny versions to indicate selected satellite(s)
If the screen's "small" the visualization takes up the entire view, leaving no room for UI controls nor statistics on position, etc. Users may not even know there are statistics "below the fold".
We should make the canvas height a percentage of the browser height -- adjusting on resize -- to leave room.
There are > 1000 Geosynchronous satellites and trying to render them is hard and slow, trying to display all their xyz/latlon positions makes it unusable.
Should we just show some subset, like first 50?
Can we update position data every 1/2 second or so? Some kind of JavaScript timer?
The output from the AIAA testmat.m is different from that in Miura's distribution. Miura has 7 values:
t, x, y, v, vx, vy, vz
The AIAA code has much more.
Looks like the Miura code added extra \n to the output and that explains the "extra" lines.
If I comment that out in the AIAA, the results are identical to the Miura results.
SO: restore output of the mysterious extra values in the Miura code.
Even though the SGP4 results are in ECI coords, they should still describe an ellipse in their own XYZ coord system.
Run a satellite or two's TLEs with (ideally current) date and time, calculate XYZ and velocity. Then plot just the XY on a flat HTML5 2d Canvas.
Mission, etc, perhaps from science.nasa.gov or NSSDC
With 35 Science satellites, the position data is a bit overwhelming. Perhaps simply reducing decimals is enough.
How about putting up a selector after the basic set (e.g., SMD) is chosen which allows selecting an individual satellite to focus upon? Maybe highlight it? Show details (e.g., from science.nasa.gov)? show orbit track? Change icon to shiny? Show only position data for selected satellites? highlight position data of selected satellites?
If the screen's "small" the visualization takes up the entire view, leaving no room for UI controls nor statistics on position, etc. Users may not even know there are statistics "below the fold".
We should make the canvas height a percentage of the browser height -- adjusting on resize -- to leave room.
Zoom way out, view frustum presumably culls all the information. Try to zoom back in, you can't. Notice that the updates to the positions is frozen.
Want to watch dot rotate around the earth, or better, a trail of the last N dots. How in Canvas?
From: Matney, Mark (JSC-KX111) at nasa.gov
The SGP software only gives information in Earth Centered Inertial (ECI) coordinates, so you will need to solve for the Earth orientation with time as well.
See:
http://en.wikipedia.org/wiki/Earth-centered_inertial
http://celestrak.com/columns/v02n01/
http://www.mathworks.com/help/toolbox/aeroblks/f3-22568.html
Hard math: http://onlinelibrary.wiley.com/doi/10.1002/0471200719.app0c/pdf
Check the Miura code stack and see if there are PREDICT integrations.
Check various 'predict' implementations and see if they use SGP4.
Probably should move the globals from twoline2rv to sgp4init, closer to initl().
I presume the MATLAB code at one point called getgravc() and set all the returns as globals so it's only called once. But it's not an expensive call.
But initl() doesn't have 'whichconst' so it can't call getgravc() itself.
This is horrid structure and the reliance on globals makes debugging very difficult.
billboards.get(sat_idx).setScale(2). Or set the color.
But how/when do we do that? How do we get the billboards? Or do we have to do it in the loop after looking at some setting set by a picker menu change event?
depends on sgp4; getgravc, dpper, dscom, dsinit, inil
Currently the immutable TLE strings are maniuplated by a icky setCharAt() which (must) returns a new string.
Instead, convert string to array, manipulate, then convert back to string. Then we can ditch setCharAt()
Now that we're plotting X,Z, we should indicate distance from viewer by dimming or shrinking the dot.
Maybe also fix for multi-collection pickign?
We change color and double size, but if the satellite's on the other side of the globe, we won't notice.
Fly to its position and zoom out enough we can see it.
We only want to do this once, when the satellite is first picked, so we can watch it travel across the globe. That is, we don't want to do this in the position loop and constantly update our position to be above the satellite so it appears motionless (with the earth spinning below it).
As of fcfdd7f Tests eighteen and twenty-five are not passing for some params despite huge tolerances.
This suggests a bug in the implementation of the rv2coe code, or perhaps something in the functions it invokes (which may not be tested rigorously enough): mag, cross, angl, newtonnu.
It's not going to be easy to test this.
like JTrack3d and n2yo.com.
Also, from TLE or other source:
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