I'm working on a java applet that simulates the MRO trajectory. It "works on my machine" but I think it breaks on other platforms. One issue is that it requires the Java runtime environment JRE1.5 & will fail on JRE1.4. Could someone here try it and say whether it worked for them or not? Here's the link:

MRO Applet

Clicking on the "RUN" button causes the timescale to speed up.

Thanks,
Joe

There's a background of Mars craters, a grey window within it and no run button at all.

So it doesn't work on my station.

Marcel.

Works fine with Win XP, Firefox & Java 1.5 on my machine.

Very useful toy.
Here works fine with the Java versión 1.5.0 (build 1.5.0-b64).

Rodolfo

It works on my WIN98, 500Mhz machine. Java 1.5

Thanks for checking it out, folks. I guess the main issue is that it doesn't run on pre-JRE1.5 systems.

Joe

Joe,
you may be the guy to ask or anyone else out there who can point me to a spot to go... I sent a question (similar to below) to marsoutreach@jpl.nasa.gov as listed on the MRO website (who knows if or when I'll get a response.. ) but your applet seems to answer it. How accurate are your orbital speeds at closest approach before orbital insertion?
BTW great applet..I'm doing something similar in Delphi. If I may suggest...Be great to add a pause button in there as well.
cheers
jb

Jim, did not work for me (running JRE 1.4.2, so no surprise; the platform is XP SP2, 1.2Ghz).

Likewise - I get the following error which seems to indicate that there's a version check failing.
Using JRE version 1.4.2_08 Java HotSpot™ Client VM
java.lang.UnsupportedClassVersionError: mroApplet (Unsupported major.minor version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at sun.applet.AppletClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.applet.AppletClassLoader.loadCode(Unknown Source)
at sun.applet.AppletPanel.createApplet(Unknown Source)
at sun.plugin.AppletViewer.createApplet(Unknown Source)
at sun.applet.AppletPanel.runLoader(Unknown Source)
at sun.applet.AppletPanel.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)

It's not usually a good idea to rely on press release info for hard numbers. For velocities one always has to ask "relative to what?" MRO should be moving at something like Mars' escape velocity near MOI relative to Mars. That's about 5 km/sec. MOI delta-V is about 1 km/sec. The capture orbit is 300 km x 45000 km with a period of about 35 hours. MOI is not an instantaneous impulse, but if you figured out the periapsis speed of the capture orbit and added 1 km/sec you should get roughly the velocity at MOI. I leave the math as an exercise for the student

As do I... just nice to know with the approximations used, how close it is to actual...
QED is used to often sometimes

Helvick, & Nprev. As the author has told that the Java applet only works with ones of the version 1.5.0 or above. You can upgrade the Java by downloading from http://www.java.com.

Rodolfo

Sorry for the delay... hadn't checked this thread in a while. As for the speed, I think the applet is accurate as it relies on the SPICE navigation information released by JPL/NAIF. That said, every time they adjust the trajectory they release new SPICE kernels and I haven't updated them in a while, so there might be a slight difference based on the current situation.

np for the delay.. You have the web page handy for the kernels. Did a quick search with no luck for mro. How "easy" is the data to read?
appreciate the info...
cheers
jb

Not easy at all really. The files are in binary form and can only be read by writing programs that make the appropriate library calls. On the other hand, NASA has a lot of tutorials explaining how to do so. See the NAIF website at http://naif.jpl.nasa.gov/naif/pds.html

The MRO kernels are at ftp://naif.jpl.nasa.gov/pub/naif/MRO/kernels/

Very true. You might be better off using JPL Horizons, which can generate ephemeris information on MRO -- http://ssd.jpl.nasa.gov/horizons.html

Of course, you can only generate heliocentric states with it, so you can't directly look at velocities in the Mars frame.

thanks for the links..once the semesters over I'll dive into it..
cheers
jb

Works fine on my MS Windows 2000 server ( 2.4 GHz Pentium IV )

I appreciate the applet that you've shared. However, I have a question relating to this view.

When comparing your homepage to the MRO Site Solar System Simulator, it appears that the MRO site simulator is not being updated. Is this just due to a wide field of vision on the MRO site, or is it actually not updating? I recall other NASA Solar System Simulators showing distance measurement and field of vision in degrees.

Thanks,

crabbsaline

Not sure what dicrepancy you're referring to... the field-of-view at the http://marsrecon.com site is 1.14 degrees (the HiRISE FOV) so the view will be very magnified, if that's the issue. The range is currently about 2.7 million km, which I think is correct.

Hi jmknapp,

Sorry for the confusion. I don't think there is a discrepancy with your homepage. Rather, I'm uncertain if there is something wrong with the MRO simulator site. I had been wondering about this before I saw your applet. Your applet seems to be reinforcing that perception.

On the JPL MRO site, other views of the MRO simulator appear to be live simulations. It's just the "Mars Reconnaissance Orbiter's View of Mars" that I am questioning.

I guess if Mars still looks like a speck on March 10, then I'll know for sure

After I sent that reply, I noticed that they are getting that image from a subdirectory of mgs:

http ://mars1.jpl.nasa.gov/mgs/realtime/mro3.jpg

Weird.

Hi again,

Looks like they are updating the image, because the surface features in their closeup view of Mars matches what I get, as does the position of Phobos. I guess they are using a wide field of view in the main image making Mars appear only as a speck. It's true that as MRO approaches Mars on the 10th the field of view I'm using (1.14 degrees) will really be zoomed in on a tiny area of the surface, so maybe a wider field of view is called for at that time. For now, seeing Mars as it would be seen by HiRise (although 512 pixels across rather than 20,000!) is a bit more interesting IMO. Funny as you say that the image is in an MGS directory.

Closest approach will be over the night side, making rendering at that point rather easy.

Thanks for taking a look into it. Glad to hear that the site is accurate.

Good luck with the rendering the nightside. Remember: #000000

Not showing access to your applet now

However, I'm still enjoying the image on your homepage. It's been fun watching this from the HiRise point of view.

Out of curiousity, I tried to imagine what the field of vision would be to the human eye. Assuming a 20 inch distance from viewer to monitor, and measuring 6.375 inches wide for your hompage simulation image, I figured that the field of vision was 18°.

Seem about right? It's been about 20 years since I've used trig.

I changed the main page a couple weeks ago, but you can still get the applet at MRO trajectory applet.



Sounds right. I think a normal human FOV is about 110 degrees, so this would be about a 6x view. Then again, the Moon for example always looks smaller in a 50mm lens photo than with the naked eye--some trick of perception.

In timeline at marsrecon.com,

Are you sure the altitude at arrival will be 428 km? Since my calculation at JPL Horizons gave 329 km above the surface.

The Horizons website is using the SPK kernel file MRO_p_c_ref-od010_050812_060401_p-v1 whereas I'm using spk_moi_ideal_051123_060320_p-v1.bsp. The latter was released on Feb. 15 & I believe represents the latest information, but who knows. During the press conference a couple weeks ago I think someone on the panel mentioned that the closest approach would be "500 km"--just to muddy the waters further!

The predict after TCM2 for closest approach during MOI was a little over 500 km. Note that the periapsis on the next orbit is typically lower by something like 80 km. They can raise this with a maneuver near the first apoapsis if needed.

MGS had a nice viewer that showed it's current altitude and location along it's orbit. As it aerobraked you could see the apoapsis being lowered, orbit by orbit. I think they even had 'predicted next' apoapsis before each aerobrake maneuver and you could see what the result was a few hours later. Any such app/link running yet for MRO?

I was wondering the same thing and was hoping to see a reply here. I guess not......