Ephemerides, Star Charts, Orbital Elements

Ephemerides

The following ephemerides (for Vesta, but the others are similar) were generated using the JPL HORIZONS system web-interface using the following settings:
Ephemeris Type: OBSERVER
Target Body: Asteroid 4 Vesta
Observer Location: Geocentric [500]
Time Span: Start=2007-03-01, Stop=2007-09-30, Step=1 h
Table Settings: QUANTITIES=1,8,9,19,20,24

Users may wish to generate an ephemeris for their specific location and only for the times when the asteroid is above their local horizon and it is dark. Check out our sample ephemeris to learn how to read and interpret these files.

[These are text files. For printing, you may want to use landscape mode.]

Vesta	Ceres	Hartley 2	Other targets?
May 2008 Jun 2008 Jul 2008 Aug 2008 Sep 2008 Oct 2008 Nov 2008 Dec 2008 Jan 2009	Ceres is on the far side of the sun and not visible. Check back in Aug.	Although just past opposition, H2 is just past its aphelion which is still outside of Jupiter's orbit, so the comet is extremely faint.	Dawn asteroids Deep Impact asteroids UM asteroids prev mission targets

---

Star Charts

Table 1: Charts for finding Vesta May-??? 2008.

---

Orbital Elements

Table 2: Table containing the orbital elements for Vesta, Ceres and Hartley 2 for input into personal planetarium programs.

---

Other Targets to Observe

Although Vesta and Ceres are the targets of the Dawn mission and Hartley 2 the target of the EPOXI mission, there are other asteroids and comets related to the missions that you might want to try to observe! Scientists, engineers, and other staff associated with the missions have asteroids named after them for recognition of work done in the field. And what about Tempel 1, the orginal Deep Impact target or comet Boethin the original EPOXI target? Well, here are the links to get you started. Just use what you've learned about observing Vesta and Ceres and apply it to these.

Dawn asteroids	Deep Impact/EPOXI asteroids	UM asteroids	previous mission targets other asteroids of interest
	2710 Veverka 2956 Yeomans 3066 McFadden 3192 A'Hearn 3498 Belton 3742 Sunshine 4201 Orosz 4958 Wellnitz 6135 Billowen 8086 Peterthomas 8216 Melosh 8262 Carcich 9251 Harch 12226 Caseylisse 12527 Anneraugh 16255 Hampton 16280 Groussin 16946 Farnham 16952 Peteschultz 16958 Klaasen 16975 Delamere 16986 Archivestef 17195 Jimrichardson 17196 Mastrodemos 18106 Blume 21450 Kissel	2956 Yeomans 3066 McFadden 3192 A'Hearn 3536 Schleicher 3742 Sunshine 4201 Orosz 4958 Wellnitz 12225 Yanfernandez 12226 Caseylisse 12494 Doughamilton 12517 Grayzeck 12527 Anneraugh 12566 Derichardson 12859 Marlamoore 12871 Samarasinha 13001 Woodney 13723 Kolokolova 16280 Groussin 16946 Farnham 16986 Archivestef	9P/Tempel 1 85P/Boethin 81P/Wild 2 19P/Borrelly 433 Eros 3327 Campins 4019 Klavetter 5504 Lanzerotti 12870 Rolandmeier 13249 Marcallen 14395 Tommorgan 32569 Deming

---

Orbital Elements for Spacecraft

The Dawn spacecraft is currently too faint to see. The EPOXI spacecraft had a flyby of Earth on 31 Dec 2007 (and will have 2 more in 2008 and 2009).

On occasion we have provided the elements for spacecraft, but they would be for a given date. Why? When looking for the elements, I found (using the telnet option at Horizons) the elements, but it gave them to me for every day that I had specified during a timespan. So I asked...

Q: Okay, if I'm understanding the output right, the elements for the spacecraft are actually changing continuously so there's not exactly one definitive set of elements?

A: Yes, that's correct. Osculating elements can only represent the position and velocity at one instant.

The spacecraft is continuously acted on by gravity perturbations, solar radiation pressure, maneuvers, etc. Six orbital elements at some instant can't capture this time evolution.

Horizons internally uses the navigation team's trajectory model, which includes such factors. So when you obtain orbital elements over a span of time, each set is the result of accessing the underlying trajectory and converting the instantaneous state into equivalent orbital elements for that instant.

Aside from thruster events (maneuvers), the delta should be small. Suitability depends on how accurate you want the result to be.
Jon G.

About orbital elements

• from SSD
• from NASA's Human Space Flight

Useful Websites

• Near Earth Object Program: graphical orbit displays of comets and asteroids, orbital elements
• Solar System Simulator: Show X as seen from Y (ie, show me Earth as seen from the DI spacecraft).
• Solar System Dynamics: various tools including Horizons ephemeris generator, orbital elements
• Minor Planet Center: various tools including ephemeris generator, orbital elements