Re: [find_orb] A Couple of Questions about Find_Orb...

Bill Gray Sep 19, 2016

Hi Andrew,

Tackling the second question first: if you put "Ven" in as an
MPC code (not as a latitude), you should get a Venericentric
ephemeris.

I do need to update the documentation on constraints. I started
out with only a few; the newer ones aren't mentioned anywhere.

Available constraints are :

q=(number) (units default to AU for these three)
Q=(number)
a=(number)

With these, you can add 'k' to indicate a constraint in kilometers; for
example, for a geostationary satellite, you might say a=42164k. (You'll
be able to use a=42164 km or a=42164km in the next version I post.)

e=(number) (dimensionless)

i=(number) (these three are all in degrees)
O=(number)
o=(number)

i = inclination, O = Omega = ascending node, o = omega = argument
of periapsis.

n=(number) (mean motion, in degrees/day)
P=(number) (default unit is years)

With the orbital period, you can add 'd' to indicate days, 'h'
for hours, 'm' for minutes. So "P=1436m" (i.e., one sidereal day)
would be about right for a geosat.

A=(number) (area/mass, in m^2/kg)
T=(date) (date/time of perihelion)

As with other time entry in Find_Orb (epoch, ephemeris starting times),
this is very flexible; the possible formats are described at

http://projectpluto.com/update8d.htm#time_entry

K=(number)
G=(number)

These are the comet and asteroid magnitude slope parameters, respectively.
K defaults to 10; G defaults to 0.15.

-- Bill

On 2016-09-19 17:36, 'Andrew Lowe' andrewlowe@... [find_orb] wrote:
>
>
> Hi Bill,
>
> I've been working with the latest release (2016 March 12) of Find_Orb for a while, and
> have a couple of questions:
>
> 1. For contrained orbits, can you preselect any of the individual parameters? For
> example, I'd like to work with an assumed argument of perihelion, but neither "w" nor
> "peri" seem to work... could you add a listing of all constrainable parameters (and
> their abbreviations) to your writeup on find_orb at projectpluto.com?
>
> 2. When creating an ephemeris, you can enter a three-character MPC observatory code in
> the latitude box to get ephemerides from that location, i.e., entering "Ven" will give
> you Venus-centered coordinates. While this worked for me in previous releases, I can't
> get it to work anymore. Has something changed in the latest release, or am I doing
> something wrong?
>
> Thanks!
>
> Andrew
> http://members.shaw.ca/andrewlowe/home.htm
>
>
>
>
>
>