[X] My Assistant

[jmknapp]

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

[stewjack]

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

[jmknapp]

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

Joe

[jabe]

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

I'm a high school physics teacher and a huge space buff and the last few years I have the students do an assignment on how you get to another planet.  I try to compare the results we calculate to the actual ones.  So I often search the site for the data.  I looked at http://mars.jpl.nasa.gov/mro/mission/tl_moi.html for the speed at which the probe arrives at and it says

As the orbiter approaches Mars in March, 2006, it will pass under the southern hemisphere at an altitude of about 300 kilometers (190 miles), traveling at about 3 kilometers per second

Is there any way to get confirmation these numbers are correct?
The 3 km/s I think is referring to the final velocity in circular orbit.  In class we figured we would be arriving at mars at 5.48 km/s when it is at an altitude of 300 km.  A delta v of 840 m/s gives the probe the desired highly elliptical orbit...  which seems to match the 1.0 km/s as noted on the web page.
Be great to know if what I'm telling the  kids is right for a change   or I need to find out where I made my mistake.  Hoping the former...
I know you guys are busy but semester is soon over and be great to let them know how close we actually were despite the approximations used.

Great web pages..love the updates posted for all the JPL sites.

Best of luck with the MOI..

cheers,
JB

[jmknapp]

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?

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.

[jabe]

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

[jmknapp]

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?

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/

[mcaplinger]

Not easy at all really.

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.