2020-06-24, 05:20 AM
Hi,
The green/red is the indicator that one of your subscriptions has been undated. Click on it to see which one. I update the novae/supernovae regularly.
Regarding the asteroids, I am sorry, but don't have your answers. I am confident that SkyTools is plotting orbits accurately, given an accurate orbit. Under normal circumstances, the NEA Today orbital elements reflect the most recent observations, and are also calculated for an epoch at the current date. But the MPC is having trouble right now because of the pandemic. The telescopes on Mount Lemon have been evacuated because of a wild fire. It is important to understand that most close approaching asteroids need constant monitoring in order to continuously refine the orbit.
I see no reason to assume that HORIZONS is more accurate. The normal advantage of HORIZONS is that it does the orbital calculations necessary to produce a position independent from the limitations of osculating orbital elements, which lose accuracy over time. But keep in mind that the special NEA Today elements are supposed to accomplish the exact same thing. The discrepancy means that either the data from the MPC or JPL has not been updated to reflect the latest observations. For all we know, neither of them have been. Consider that the MPC is where everyone sends their observations for analysis and the MPC is specifically tasked with tracking near earth asteroids. So as far as I know, HORIZONS is actually dependent on the MPC for updated data. It is possible that they have direct data pipelines from some of the big surveys, but I doubt it.
Previous experience does not seem to apply in the current situation. If you really want to know which one is generating the correct positions, your best bet is to compare to actual observations, or to ask the MPC or JPL. Another possibility is to get on the MMPL listserv and ask the knowledgeable people there, many of whom are part of the professional asteroid community.
The green/red is the indicator that one of your subscriptions has been undated. Click on it to see which one. I update the novae/supernovae regularly.
Regarding the asteroids, I am sorry, but don't have your answers. I am confident that SkyTools is plotting orbits accurately, given an accurate orbit. Under normal circumstances, the NEA Today orbital elements reflect the most recent observations, and are also calculated for an epoch at the current date. But the MPC is having trouble right now because of the pandemic. The telescopes on Mount Lemon have been evacuated because of a wild fire. It is important to understand that most close approaching asteroids need constant monitoring in order to continuously refine the orbit.
I see no reason to assume that HORIZONS is more accurate. The normal advantage of HORIZONS is that it does the orbital calculations necessary to produce a position independent from the limitations of osculating orbital elements, which lose accuracy over time. But keep in mind that the special NEA Today elements are supposed to accomplish the exact same thing. The discrepancy means that either the data from the MPC or JPL has not been updated to reflect the latest observations. For all we know, neither of them have been. Consider that the MPC is where everyone sends their observations for analysis and the MPC is specifically tasked with tracking near earth asteroids. So as far as I know, HORIZONS is actually dependent on the MPC for updated data. It is possible that they have direct data pipelines from some of the big surveys, but I doubt it.
Previous experience does not seem to apply in the current situation. If you really want to know which one is generating the correct positions, your best bet is to compare to actual observations, or to ask the MPC or JPL. Another possibility is to get on the MMPL listserv and ask the knowledgeable people there, many of whom are part of the professional asteroid community.
Clear skies,
Greg
Head Dude at Skyhound
Greg
Head Dude at Skyhound