News "Plymouth Rock" Asteroid Mission

[Wishbone]

Update: got the state vectors from 2001 to 2050, but now I have to figure out how to run the MKSPK utility...

EDIT: uploaded the kernel attached to the post. Haven't tried it myself yet...

 

[Wishbone]

Here is the input file given to MKSPK:

\begindata
INPUT_DATA_TYPE   = 'STATES'
OBJECT_ID = 3405189
OUTPUT_SPK_TYPE   = 12
OBJECT_NAME       = '(2008 EA9)'
TIME_WRAPPER = '# JD TDB'
CENTER_ID         = 0
CENTER_NAME       = 'SOLAR SYSTEM BARYCENTER'
REF_FRAME_NAME    = 'J2000'
LINES_PER_RECORD  = 1
POLYNOM_DEGREE    = 7
INPUT_DATA_UNITS  = ('DISTANCES=km')
PRODUCER_ID       = 'JPL Horizons'
DATA_ORDER        = 'epoch x y z vx vy vz'
DATA_DELIMITER    = ','
LEAPSECONDS_FILE  = 'naif0009.tls'
PCK_FILE          = 'gravity.tpc'
SEGMENT_ID        = 'SPK_ELEMENTS_12'
\begintext

To get the data, sent the following e-mail to
[email protected] (Subject line was "JOB" (without quotes)

!$$SOF
COMMAND= 'DES=2008 EA9'
EMAIL_ADDR = ' '
TABLE_TYPE = 'VECTORS'
REF_PLANE = 'ECLIPTIC'
START_TIME = '2001-JAN-1 10:00'
STOP_TIME = '2031-JAN-1 10:00'
STEP_SIZE = '1 d'
REF_SYSTEM = 'J2000'
OUT_UNITS = 'KM-S'
RANGE_UNITS= 'KM'
VECT_TABLE = '2'
VECT_CORR = 'NONE'
!$$EOF

 

[Tychonaut]

Update: got the state vectors from 2001 to 2050, but now I have to figure out how to run the MKSPK utility...

EDIT: uploaded the kernel attached to the post. Haven't tried it myself yet...

Thanks for uploading this, Wishbone. :tiphat:
I tried using this with Arrowstar's [ame="http://orbithangar.com/searchid.php?ID=5418"]Trajectory Optimization Tool[/ame], and got bizarre results. Computed Earth departure C3 is 36 km^2/s^2, while the LM report gives a worst-case C3 of 4.9. I must be doing something wrong...
Almost tempted to try and find an email address for one of the Plymouth Rock authors and ask how they arrived at their numbers, but if they replied it would probably be over my head.

 

[Wishbone]

Tested the set myself and it works. The only caveat: one has to set BODY and BARYCENTER lines in the SPICE'd .cfg file equal to the asteroid's ID, which is 3405189. If you simply plug in the name, you will end up around Sedna and rotating like hell which is definitely wrong on both counts.

 

[Tychonaut]

Tested the set myself and it works. The only caveat: one has to set BODY and BARYCENTER lines in the SPICE'd .cfg file equal to the asteroid's ID, which is 3405189. If you simply plug in the name, you will end up around Sedna and rotating like hell which is definitely wrong on both counts.

Pardon my ignorance, but I am just more confused now...which cfg file contains these lines? They don't appear in the Orbiter config file or the MPCORB database so far as I can see, and TrajOptTool seems to know the asteroid only by its number.

 

[Wishbone]

If you want the real ephemerides to show up in Orbiter, you have to use Ajaja's spice.dll (http://www.orbiter-forum.com/showthread.php?t=1387&page=3).
The first lines in 2008 EA9.cfg file would look like this:

Name = 2008 EA9
Module = spice
Kernel = Kernels\2008ea9.bsp
Barycenter = 3405189
Body = 3405189
Origin = SUN BARYCENTER

...with the rest of the data on mass, size and period etc. taken from the database.

 

[Tychonaut]

If you want the real ephemerides to show up in Orbiter, you have to use Ajaja's spice.dll (http://www.orbiter-forum.com/showthread.php?t=1387&page=3).
The first lines in 2008 EA9.cfg file would look like this:

Name = 2008 EA9
Module = spice
Kernel = Kernels\2008ea9.bsp
Barycenter = 3405189
Body = 3405189
Origin = SUN BARYCENTER

...with the rest of the data on mass, size and period etc. taken from the database.

Aha, thanks, I didn't know spice.dll existed. I will give it a try. :tiphat:

Tried installing the Spice Revisited package and using a cfg file as specified above, to no avail. Though Body and Barycenter lines are as specified, I get the Sedna-like orbit you mentioned for 2008 EA9. Still no idea how to get it working. Were you actually able to plot a sensible transfer orbit to 2008 EA9 once you got it working using spice?

 

[Wishbone]

Interesting. I'll try it some time this week, in IMFD. Will keep you posted.

 

[Wishbone]

Managed to launch on a trajectory to the asteroid with cue from Arrowstar's TOpTool. Attaching a save, and the config files I'm using.

 

[Tychonaut]

Managed to launch on a trajectory to the asteroid with cue from Arrowstar's TOpTool. Attaching a save, and the config files I'm using.

Thanks! I will give this a try when I have a chance and see if I get any farther...like out of LEO.
:tiphat:

Well, I tried the config files and I still get nonsense values for 2008 EA9's orbital elements within Orbiter. Perhaps I've tinkered too much or added one too many addons which is somehow messing things up. At some point I may try again with a fresh Orbiter install and see if it works any better.