OHM Trajectory Optimization Tool v2.1

[boogabooga]

So, two years ago I used the JPL HORIZONS system (http://ssd.jpl.nasa.gov/?horizons) to download the ephemeris file to add Sedna for use in this program. The conversation can be found here: http://www.orbiter-forum.com/showthread.php?t=31990

At that time, I added my e-mail address to their contact list. Today I got the following e-mail which I wanted to document here in case it might be useful to users of this program in the future.

Jon D. Giorgini  Aug 22 at 11:39 PM
To	
[[COLOR="Red"]Redacted by boogabooga[/COLOR]]
Who can stop reading:
---------------------
This email can be skipped if you do not use asteroid and comet small-body 
SPK files generated by the JPL Horizons server, or know that software which 
uses such SPK files has been built using version N0065 or later of the SPICE 
Toolkit library. 

Purpose:
--------
Asteroid and comet SPK trajectory files produced by the JPL Horizons 
system will be changed from the current Type 1 format to a new Type 21 
format. 

The new format offers higher-fidelity reproduction of the trajectory 
in some situations, primarily for close planetary encounters and over 
long time-spans. 

Use of the new trajectory files requires that application software be 
re-linked to incorporate a new library reader but with no other changes 
to user software.

SPK files for other classes of bodies are not affected, only asteroids 
and comets from Horizons.

Contacts:
---------
(1) This notice is being sent to email addresses supplied to Horizons 
by users over the last three years when generating small-body SPK files.

(2) Notice is being sent to internal JPL groups likely to have relevant 
software and users.

(3) The NAIF Group recently sent a notice to subscribers of their SPICE 
Announce mailing list.

(4) Some known developers have been contacted over the last year regarding 
the change, since notice-of-intent was first posted in the Horizons system 
news July 23, 2014 and then again on March 2 of 2015:

  http://ssd.jpl.nasa.gov/?horizons_news 

So you might receive more notice of this issue than you need, depending 
on the extent your email address overlaps these lists.

Details
-------
A reader for the new file format was first included in the N0065 SPICE 
Toolkit released by the NAIF Group in July 2014.

To use comet and asteroid SPK files generated by Horizons after the 
format becomes active, software which reads small-body SPK files needs 
to be re-linked against SPICE library version N0065 or greater. 

No other change to user software beyond re-linking with the latest 
SPICE Toolkit library to produce new executables is required.

The NAIF Group's Toolkit software is available here:

  http://naif.jpl.nasa.gov/naif/toolkit.html

If user software is re-linked with the above N0065+ library, it will 
automatically have access to the new reader and automatically use the 
new file structure when the change becomes active, without additional 
effort by users. 

If not re-linked, user software will fail when trying to read the new 
small-body SPK file format. Old/current Type 1 SPK files will NOT be 
affected and so existing files will continue to be transparently readable.

Example files in both the current/old format and forthcoming new format 
can be retrieved for testing from the anonymous FTP site:

  ftp://ssd.jpl.nasa.gov/pub/xfr/example_type-01_OLD_smb.bsp

  ftp://ssd.jpl.nasa.gov/pub/xfr/example_type-21_NEW_smb.bsp

The switch-date is not fixed; this email is primarily to inform and 
accept potential feedback from key users. If a change after September 
could present a problem, let me know.

-------------------------------------------------------------------------------
Jon Giorgini                      |  Navigation & Mission Design Section
Senior Analyst                    |  Solar System Dynamics Group
[email protected]        |  Jet Propulsion Laboratory
-------------------------------------------------------------------------------

I'm not sure if it means that the new SPK files will not be compatible with this program?

 

[cristiapi]

I'm not sure if it means that the new SPK files will not be compatible with this program?

Your question seems well explained in the section "Details":

To use comet and asteroid SPK files generated by Horizons after the 
format becomes active, software which reads small-body SPK files needs 
to be re-linked against SPICE library version N0065 or greater. 
[...]
If not re-linked, user software will fail when trying to read the new 
small-body SPK file format. Old/current Type 1 SPK files will NOT be 
affected and so existing files will continue to be transparently readable.

Since this add-on has been published 4 years ago, surely it has been built with an older version of SPICE and hence the new SPK file won't be compatible with this add-on.

 

[boogabooga]

Okay, it's time to see what others think about this issue.

I've run an optimization on an Earth, Venus,Venus, Earth, Jupiter mission plan. I get this output:

OPTIMUM EARTH DEPARTURE DATE: 10/17/2018 20:54:39 - C3: 16.8373 km²/sec²                                                                    
OPTIMUM VENUS SWINGBY DATE: 3/28/2019 20:24:29 - Powered Delta-V Required: 26.2004 km/sec                          
OPTIMUM VENUS SWINGBY DATE: 5/26/2020 20:25:48 - Powered Delta-V Required: 0.0097167 km/sec	             
OPTIMUM EARTH SWINGBY DATE: 3/4/2021 11:17:34 - [B]Powered Delta-V Required: 147.1112 km/sec	[/B]           
OPTIMUM JUPITER BARYCENTER ARRIVAL DATE: 4/6/2023 1:59:32 - Body-centric Arrival Velocity: 7.0973 km/sec

I'm having difficulty getting this in TransX. Specifically, what is meant by Powered Delta-V Required: 147.1112 km/sec? :huh:

Seriously? I can't possibly imagine that that means I need to make a periapsis burn of
147 111.2 m/s. That over three times escape velocity from the solar system. Yet the trajectory of the last Earth-Jupiter leg is clearly elliptical:

LEG 4 (Number of Full Revolutions: 0)
-Semi-major Axis: 449274907.6539983 km
-Eccentricity: 0.7140858
-Inclination: 2.1262526 deg
-Long. of Ascending Node: 163.8300975 deg
-Argument of Periapse: 47.2839797 deg
-True Anomaly (start): 312.6985108 deg
-True Anomaly (end): 169.8103767 deg

Is it simply that the units are mislabeled and he means 147 m/s or 147 dam/s (1470m/s)? Or does this actually refer to the energy in km^2 / s^2? Does anyone have an interpretation of this?