[X] My Assistant

[dmuller]

I am in the midst of programming a rather simple javascript to keep track of Phoenix's progress (and later EDL) together with a timeline of events. The current version is online at www.dmuller.net/phoenix, but if anybody has more details, I would greatly appreciate any input, in particular of upcoming events and their anticipated timing, as well as details during the atmospheric flight (altitude, speed, downrange). For all times, it would also be great to know their timezone and whether they are SCET or ERT. The "positions" information is calculated based on data downloaded from the SSD Horizons system, which is available right up to the Entry Interface.

Naturally, I also welcome any suggestions on what other information could be added to the script.

I can also provide an off-line version of the script (does not require php) e.g. for public display in a visitor center.

Please post any information / feedback / requests either here or send me an email through my public profile on this board. I may not respond for a couple of days as I will not have internet access.

Thanks a lot to everybody!

Phoenix Entry Interface in 41 days 22 hours. Distance to fly: 79.7 million km. Altitude above Mars: 9.6 million km

[Guest_Zvezdichko_*]

Great work, I like it.

[djellison]

Now that is very very cool.

I would say this is a reasonable starting point - http://www.mps.mpg.de/images/projekte/phoe...oenix08_xxl.jpg - it is very out of date I think - but the usual round of mission press con, and then science press con can not be too far away, and updated press pdf's will get released about then, and probably an updated landing time.

The attached is a bit more up to date.

Doug

Attached thumbnail(s)

 

[dmuller]

Thanks Doug. That was the graph I was working from, though it has some shortcomings, such as the altitude referencing to MOLA and the touchdown being at altitude 0km even though the actual landing site is (as seen on the image) somewhere between 3 and 5 kms below MOLA. It also has a time elapsed of 470secs from entry interface to touchdown, which now seems to be 440 sec (+/- 30 secs).

On that note, the Canberra Deep Space Communication Complex visitor center told me at they have received information as of earlier this week that the nominal landing is on May 25, 23:53:52 UTC (+/- 30 secs) and atmospheric entry at 23:46:32 UTC (Earth Received Time). In Spacecraft Event Time, atmospheric entry is thus at 23:31:12 and landing at 23:38:32. (One-way light-time will be 920 secs)

I'll update the scripts in due course and will post a message here once that's done.

Edit: fixed error in SCET landing time

[Spirit]

Does your script predict how many Gs will the spacecraft "feel" during the descent?

[dmuller]

Does your script predict how many Gs will the spacecraft "feel" during the descent?

Unfortunately not (yet). The only information I have regarding this is the info that can be extracted from the charts above, with max deceleration being between 7 and 9 g's. I am trying to get more info from the Phoenix team / JPL, and will incorporate it into the script if I get good enough information to do so. Information on the atmospheric section of the flight (events, speed, altitude, downrange, deceleration etc) is pretty sparse at this time, and difficult to extrapolate from the little I have.

[dmuller]

An update with 22 days and 5 million kilometers to go ...

First my thanks to Emily for mentioning the simulation on her Planetary Society blog. It attracted a large crowd (avg 100 visits/day) and by now I get a steady stream of visitors to the simulation from people who have bookmarked the site. Great!

As for the script, all functionality is now included, including DSN coverage, virtual commentary during landing and a bigger font for the numbers. At the moment, the script is in "Spacecraf Event Time", and "Earth Received Time" will be enabled shortly.

The challenge now is to fine-tune the data during the first part of the atmospheric flight, in particular from Entry Interface to Parachute deployment. Therefore, again, if anybody has information on the following, please share them with me ... pretty please ...

(1) Precise timing for TCMs 4, 5, 6 and 6X

(2) Anticipated nominal altitude as a function of time and speed as a function of time (time being from Entry Interface or landing). Trajectory reconstructions for Spirit, Opportunity or Beagle-2 would be welcomed too ... I saw references made to them on the net, but havent actually found one :-( I did, however, find a neat one for the Huygens landing on Titan

Piecing together the snippets of interviews found on youtube just doesnt give the whole picture.

Also, if you manage / work for / represent etc a spaceflight educational outreach position (and dont have internet access there), I can create an offline version of the script. At last count, it's already heading that way to 3 such organizations on 3 continents.

[Guest_Zvezdichko_*]

I'm unable to open the web site ;(

[dmuller]

I'm unable to open the web site ;(

Hmmm it works for me. Maybe you hit a busy spot? Try again at http://www.dmuller.net/phoenix

[jamescanvin]

I've had no problems accessing the site from work but just tried it at home now and I get a "Failed to open page".

[dmuller]

Looks like the host server has problems as I cant access the page now either and the host's own webpages are very slow. Better now than in 3 weeks. Anyway, I will arrange for a mirror site with a different host and advertise it here once it's up and running in a couple of days ... planned to do that anyway but not so early on.
Daniel

[kwan3217]

...The challenge now is to fine-tune the data during the first part of the atmospheric flight, in particular from Entry Interface to Parachute deployment. Therefore, again, if anybody has information on the following, please share them with me ... pretty please ...

(2) Anticipated nominal altitude as a function of time and speed as a function of time (time being from Entry Interface or landing). Trajectory reconstructions for Spirit, Opportunity or Beagle-2 would be welcomed too ... I saw references made to them on the net, but havent actually found one :-( I did, however, find a neat one for the Huygens landing on Titan

http://trs-new.jpl.nasa.gov/dspace/bitstre...8/1/05-2473.pdf "Landing on Mars" with a velocity vs altitude chart for all the past and current entry phase stuff. You could integrate it somehow to get downrange vs time, then the things you want.

http://ntrs.nasa.gov/archive/nasa/casi.ntr..._2008012906.pdf "2007 Mars Phoenix EDL Simulation and Modeling Analysis" Another velocity vs altitude chart.

http://trs-new.jpl.nasa.gov/dspace/bitstre...7/1/95-0980.pdf "Mars Pathfinder Atmospheric Entry Trajectory Design" includes an altitude and acceleration as function of time from entry interface. For Mars Pathfinder, so not particularly relevant.

All of these references say that Phoenix is similar to MER entry trajectory, which is very well documented (search ntrs.nasa.gov).

http://starbrite.jpl.nasa.gov/pds-explorer...ume=merimu_1001 Mars Exploration Rover EDL accelerometer record

I've seen acceleration and velocity vs time from entry interface charts, but I can't locate them again.

I'm working on a Phoenix model for Orbiter http://orbitersim.com and it looks like I have a valid aerodynamic and atmosphere model, since it is hitting exactly 9.2G peak on entry. I'll be able to get an extraordinarily complete log of my model's entry. I plan on publishing the model before the real thing does its entry.

[dmuller]

Thanks Kwan for the links. Interesting reading, and please do make the orbitersim.com Phoenix model available for public use :-)

Meanwhile, the following animation has been put up at http://phoenix.lpl.arizona.edu/videos.php#edl_hud, very useful for my project, and impressive as is:

Phoenix EDL Animation - This animation featuring a heads-up display shows second-by second the entry, descent and landing of the Phoenix Mars Lander on May 25, 2008. The animation was created by NASA's Jet Propulsion Laboratory's Solar System Visualization Project.
Low Bandwidth English Units (5.7 MB)
Low Bandwidth Metric Units (5.7 MB)
High Bandwidth English Units (47.3 MB)
High Bandwidth Metric Units (42.9 MB)

I will still use your references for the time from Entry Interface to plasma blackout.

Daniel

[dmuller]

With 4 1/2 days to landing, and after 3,500 website visits (a lot for a website of mine) I can announce that the final version of the real-time simulation is now online at http://www.dmuller.net/phoenix. I do not intend to make further changes unless the entry interface and/or nominal landing times change "significantly". Such changes can be made as late as just after TCM 6. Some important information:

Download Speed: I would expect the simulation to take longer to load on May 25. At the moment, all position data is correct on an hourly basis and interpolated in between, but soon this will change to a minute-by-minute basis and requires more data to be loaded into the simulation. Starting from about 30 minutes before landing, all the remaining trajectory information will be loaded into the script when it does its auto-reload, or is accessed for the first time. This may take a while longer than usual, but avoids having to reload the script during the crucial EDL phase. Be patient :-)

Mirror Site: In case anything goes pear-shaped, the simulation is also running at http://www.dmuller.com/phoenix. You can use this site if the main page goes down or becomes too slow. I will not be able to attend to the script or server issues in the last 24 hours before landing as I wont be home, and the server sits in the US where there is a long weekend. On that note: could anybody record the NASA TV feed for me (preferably the one without commentary) ... I'll paypal for postage etc?

Beyond Phoenix: given the interest in the script and feedback I have received, I will create similar scripts in due course. However, I do need to catch up on my "proper", space-unrelated :-( work a bit before continuing (as a freelancer it's easy to 'scale back' work for other more interesting activities, but unfortunately the bank account starts to hurt a month later ...). Top of the list will be New Horizons (because I like that mission) and Messenger (for the upcoming Mercury flyby 2). Updates will be posted to where the Phoenix script sits at the moment. I will also look into creating a spaceflight (& related) outreach online library, so if anybody has any suggestions, you know where to find me.

8.5 million km to go. Good luck Phoenix, we're all waiting to hear from you from the surface of Mars.

Go, Phoenix!


Daniel

[tanjent]

One question, dmuller. I have been watching your real time simulation for several weeks now and one feature that attracts my eye is the gravitational acceleration towards Mars. I have not really been writing down the values, but I will have to start doing so because it seems to be behaving in ways that I can't understand. The masses of Mars and Phoenix are not changing, so if the distance between the two bodies is getting monotonically closer, then the gravitational acceleration should never decrease, right? But on more than one occasion I believe I have seen it do so - most recently today compared to several days ago. The first couple times, I thought it was my imagination. Am I hallucinating, or maybe just counting the significant decimals wrong, or do we have a "Phoenix Anomaly"? My knowledge of physics is very weak, but I thought there were only those three mentioned variables involved, at least in the Newtonian world.