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en:documentation:display_of_neos [2013/02/10 23:28] – [Download of the CatGen project-files] marc_fokkeren:documentation:display_of_neos [2022/06/28 14:14] (current) – [New method since version 4.3] pch
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-~~NOTOC~~+====== Display of NEOs  ======
  
-====== Display of NEOS (Near Earth Objects) ====== +====== Display of NEO during Earth transit ======
-It is possible to display NEOs in Skychart after meticulous calculation of their positions on the sky. To do these calculations, we need our position on earth and the time for moment of display. We can obtain the results of these calculations from the [[http://www.minorplanetcenter.net/iau/MPEph/MPEph.html| Minor Planet Center]] or from [[http://ssd.jpl.nasa.gov/horizons.cgi|Horizons website from NASA JPL]]. After that, we can copy the data in a ASCII text file and use CatGen to compile a catalogue. \\ We can not use the orbital elements to do a precise display of a NEO flyby!  \\ \\+
  
-It is strongly advised to do a latest calculation and compilation of the catalog short before observing. The track of the NEO is likely to be different from the earlier predictions! +This method can only work for the flyby of a well know asteroid with a good precision for the circumstance of the flyby. This is necessary for the MPC or Horizon to compute a precise perturbed orbit.\\ 
 +In the case of a newly discovered object it is better to use the other method [[#display_neo_in_need_of_confirmation|described at the bottom of this page]].
  
-==== Why we're not using orbital elements now ==== +===== New method since version 4.3 ===== 
-Usually Skychart is very well capable to create reliable charts with planets, comets and asteroids based on orbital elements. Because of the usual large distances, the perturbations caused by the gravity field of the Earth or other planets are only very small influences on the track of the solar system objects. In case of a flyby situation, the gravity of the Earth is one significant perturbator extra, it has a large influence on the trajectory.+ 
 +Since the beta version from February 2021 it is possible to compute the object position directly in the program using a SPICE kernel for the NEO (or other asteroid). Even for a perturbed orbit this method give the same precision than Horizon.\\ 
 +It automate the Horizon Telnet interface to prepare a kernel file and download it by FTP. 
 + 
 +Open Setup -> Solar System, then the tab **SPICE ephemeris** 
 + 
 +The first time you need to enter your email that is required by JPL. Enter the name of the NEO, the first day you want the position, the number of days of the prevision. \\ 
 +Do not enter a too long period here because this can increase the file size a lot, but also because the prevision is continuously updated with new observation that increase it's precision. It is easy to update the file later to extend it's validity.\\ 
 +When ready click **Download**. 
 + 
 +{{:en:documentation:neospice1.png?400|}} 
 + 
 +After the download is complete you see a new entry in the list below.\\ 
 +Be sure to select the object you want to display on the chart.\\ 
 +A mouse right click present a menu to refresh or delete one or all of the ephemeris.\\ 
 +Click **OK** at the bottom of the window. 
 + 
 +{{:en:documentation:neospice2.png?400|}} 
 + 
 +To locate the new object type the name in the search toolbar and press Enter. 
 + 
 +{{:en:documentation:neospice3.png?400|}} 
 + 
 +The display of this object is independent of the asteroid that not need to be selected.\\ 
 +There is also an independent selection available to plot the orbit path. 
 + 
 +{{:en:documentation:neospice4.png?400|}} 
 + 
 + 
 +---- 
 + 
 +===== Old method using local catalog ===== 
 + 
 +It is possible to display Near Earth Objects (NEOs) in Skychart after meticulous calculation of their positions on the sky. To do these calculations, we need our position on Earth and the time for moment of display. We can obtain the results of these calculations from the [[http://www.minorplanetcenter.net/iau/MPEph/MPEph.html| Minor Planet Center]] or from [[http://ssd.jpl.nasa.gov/horizons.cgi|Horizons website from NASA JPL]]. After that, we can copy the data in a ASCII text file and use CatGen to compile a catalogue.  
 + 
 +We can not use the orbital elements to do a trustworthy track display of a NEO flyby!  \\ 
 +**It is strongly advised to do a latest calculation and compilation of the catalog short before observing. The track of the NEO is likely to be different from the earlier predictions!** 
 + 
 + 
 +=== Why we're not using orbital elements now === 
 +Usually Skychart is very well capable to create reliable charts with comets and asteroids based on orbital elements. Because of the usual large distances, the perturbations caused by the gravity field of the Earth or other planets are only very small influences on the track of the solar system objects. In case of a flyby situation, the gravity of the Earth is one significant perturbator extra, it has a large influence on the trajectory.
    
 Orbital elements are mathematical data to determine conical section orbits (ellipses, parabola's) of solar system objects moving around the Sun. The orbital elements are calculated based on two bodies, the object itself and the Sun. Of course, there are the perturbations by the planets, but distances are very large, so influences are little. This is why we -under normal conditions- can use orbital elements to make reliable predictions for some time. Orbital elements are mathematical data to determine conical section orbits (ellipses, parabola's) of solar system objects moving around the Sun. The orbital elements are calculated based on two bodies, the object itself and the Sun. Of course, there are the perturbations by the planets, but distances are very large, so influences are little. This is why we -under normal conditions- can use orbital elements to make reliable predictions for some time.
  
 In case of NEOs, these normal conditions are not the case. To make predicitons about time and position, we need to do calculations based on three bodies: The object itself, the Sun and the Earth. Under the extra influence of Earths gravity, the track of the object does not follow its former conical section orbit anymore. Because orbital elements describe only conical sections, these aren't helpful in case of NEOs. If you would hold on to use orbital elements during a flyby event, you wil notice great changes of the orbital element data over short periods of time. Only after the object has moved far enough from Earth's influence you can rely on the orbital elements again.  In case of NEOs, these normal conditions are not the case. To make predicitons about time and position, we need to do calculations based on three bodies: The object itself, the Sun and the Earth. Under the extra influence of Earths gravity, the track of the object does not follow its former conical section orbit anymore. Because orbital elements describe only conical sections, these aren't helpful in case of NEOs. If you would hold on to use orbital elements during a flyby event, you wil notice great changes of the orbital element data over short periods of time. Only after the object has moved far enough from Earth's influence you can rely on the orbital elements again. 
-===== Download of the CatGen project-files =====+ 
 +==== Download of the CatGen project-files ====
 You can use ephemerides calculations from both the Minor Planet Center (MPC) and the NASA JPL Horizons, or you can choose one of them. Skychart is capable to display catalogues of both sources in one single chart. \\ \\ You can use ephemerides calculations from both the Minor Planet Center (MPC) and the NASA JPL Horizons, or you can choose one of them. Skychart is capable to display catalogues of both sources in one single chart. \\ \\
 For our convenience, I compiled a zip file containing: For our convenience, I compiled a zip file containing:
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 | **README.txt** | Short description of the purpose of these files.| | **README.txt** | Short description of the purpose of these files.|
  
-First of all, download [[http://www.centaurus-a.nl/home/files/ephemerides.zip|this zip file]] and save it in the directory where you want to store your catalogues. With windows, the standard catalogue directory is ''C:\Program Files\Ciel\cat'', with Linux that is ''/usr/share/apps/ciel''. +First of all, download [[https://ap-i.net/pub/skychart/neo/ephemerides.zip|this zip file]] and save it in the directory where you want to store your catalogues. With windows, the standard catalogue directory is ''C:\Program Files\Ciel\cat'', with Linux that is ''/usr/share/apps/ciel''. 
 Unzip the file in your catalogue directory. After that, you will find a new directory named ''**ephemerides**''. It will contain the above-mentioned files.  Unzip the file in your catalogue directory. After that, you will find a new directory named ''**ephemerides**''. It will contain the above-mentioned files. 
  
-===== Retrieval of Minor Planet Center data =====+==== Retrieval of Minor Planet Center data ====
 Open the source of the MPC data [[http://www.minorplanetcenter.net/iau/MPEph/MPEph.html|by this link]] in a new Window.  \\ Open the source of the MPC data [[http://www.minorplanetcenter.net/iau/MPEph/MPEph.html|by this link]] in a new Window.  \\
 Select the radio button ''**Return Ephemerides**'', in case it wasn't selected. Enter the object identification(s) in the rectangular window for which you want generate the catalogue, for example **2012 DA14**. \\ Select the radio button ''**Return Ephemerides**'', in case it wasn't selected. Enter the object identification(s) in the rectangular window for which you want generate the catalogue, for example **2012 DA14**. \\
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 If you don't want to use ephemerides data from Horizons you can savely skip the next paragraph and continue with [[en:documentation:display_of_neos#genereration_of_an_ephemerides_catalogue_with_catgen|Genereration of an ephemerides catalogue with CatGen]].  If you don't want to use ephemerides data from Horizons you can savely skip the next paragraph and continue with [[en:documentation:display_of_neos#genereration_of_an_ephemerides_catalogue_with_catgen|Genereration of an ephemerides catalogue with CatGen]]. 
  
-===== Retrieval of Horizons position data =====+==== Retrieval of Horizons position data ====
  
 Open [[http://ssd.jpl.nasa.gov/horizons.cgi|this link]] in a new window.  \\ Open [[http://ssd.jpl.nasa.gov/horizons.cgi|this link]] in a new window.  \\
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 Now open in the earlier created ''**ephemerides**'' directory the file ''**horizons.txt**'' using an ASCII-editor (i.e. notepad of vi). Select in the browser containing the generated MPC-efemerides only those lines that contain position data. Copy the lines in the horizons.txt document and save it. We are going to use this document as an //**Input catalog file**// with CatGen. \\  Now open in the earlier created ''**ephemerides**'' directory the file ''**horizons.txt**'' using an ASCII-editor (i.e. notepad of vi). Select in the browser containing the generated MPC-efemerides only those lines that contain position data. Copy the lines in the horizons.txt document and save it. We are going to use this document as an //**Input catalog file**// with CatGen. \\ 
  
-===== Genereration of an ephemerides catalogue with CatGen =====+==== Generation of an ephemerides catalogue with CatGen ==== 
 + 
 +If you keep the default file name for the data and you not want to do any change to the provided example mpc.hdr or hori.hdr you can skip this section and go directly to [[display_of_neos#activate_the_catalogue|Activate the catalogue]].
  
 For common documentation on the usage of CatGen click [[en:documentation:catgen|here]]. \\ For common documentation on the usage of CatGen click [[en:documentation:catgen|here]]. \\
  
-From the menu: **Setup → Catalog**, then the tab **Catalog** in the dialog, click the **CatGen button** at the right hand side. \\ \\ +From the menu: **Setup → Catalog**, then the tab **Catalog** in the dialog, click the **CatGen button** at the right hand side. \\  
-==== CatGen Page 1 ====+ 
 +=== CatGen Page 1 ===
 Click at the bottom of the new dialog the button **Load project**. Find the directory were you earlier unzipped the downloaded file and select the appropriate **.prj file** that belongs to the ephemerides source. \\ \\ Click at the bottom of the new dialog the button **Load project**. Find the directory were you earlier unzipped the downloaded file and select the appropriate **.prj file** that belongs to the ephemerides source. \\ \\
 Replace at **Catalog short name** the identification for a short, recognizable catalogue name, max. 4 signs. For example, the last four signs from the object name.\\ \\ Replace at **Catalog short name** the identification for a short, recognizable catalogue name, max. 4 signs. For example, the last four signs from the object name.\\ \\
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 Click **Next**.\\ \\  Click **Next**.\\ \\ 
  
-==== CatGen Page 2 ====+=== CatGen Page 2 ===
 **For MPC:** Leave equinox to 2000, set epoch to the year of the date for which you're creating the chart.\\ \\ **For MPC:** Leave equinox to 2000, set epoch to the year of the date for which you're creating the chart.\\ \\
 **For Horizons:** Find in the results part of the Horizons page the equinox and epoch data. These are displayed above the coordinates table. It is likely that you will find data as ''Initial FK5/J2000.0 heliocentric ecliptic osculating elements'', in that case, leave equinox to 2000. The epoch has been given in Julian format and as ordinary date. Take for the epoch the year part of the ordinary date. \\ \\ **For Horizons:** Find in the results part of the Horizons page the equinox and epoch data. These are displayed above the coordinates table. It is likely that you will find data as ''Initial FK5/J2000.0 heliocentric ecliptic osculating elements'', in that case, leave equinox to 2000. The epoch has been given in Julian format and as ordinary date. Take for the epoch the year part of the ordinary date. \\ \\
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 Click **Next**. \\ \\ Click **Next**. \\ \\
  
-==== CatGen Page 3 ====+=== CatGen Page 3 ===
 Here, all needed settings are in place for the formats of MPC - or Horizons data. Click **Next**.\\ \\ Here, all needed settings are in place for the formats of MPC - or Horizons data. Click **Next**.\\ \\
  
-==== CatGen Page 4 ====+=== CatGen Page 4 ===
 Now, set the path where you want to write the catalogue file. A logical place is the same directory where you placed the ASCII and .prj files. \\ Now, set the path where you want to write the catalogue file. A logical place is the same directory where you placed the ASCII and .prj files. \\
 Save your project settings by a click at the button **Save project**.\\ Save your project settings by a click at the button **Save project**.\\
 Now click the button **Create catalog**, after that, click **Close**.\\ \\ Now click the button **Create catalog**, after that, click **Close**.\\ \\
  
-Click at the button **Add** in order the tell Skychart where to find your new catalog. Search for the ''.hdr'' file of the catalogue in the directory. After that, activate the catalogue by a click at the red dot. To confirm activation, it will turn green. \\ \\+=== Activate the catalogue === 
 + 
 +From the menu: **Setup → Catalog**, then the tab **Catalog** in the dialog, click at the button **Add** in order the tell Skychart where to find your new catalog. Search for the ''.hdr'' file of the catalogue in the directory. After that, activate the catalogue by a click at the red dot. To confirm activation, it will turn green. \\ 
 +Also be sure Skychart is configured to show the Deep Sky Objects because the symbol used to draw the asteroid position are DSO symbol.\\
  
 ===== Display ===== ===== Display =====
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 +----
 +
 +
 +====== Display NEO in need of confirmation ======
 +
 +In the case there are not enough observations to be sure of the position of a newly discovered object you can use the following method developed by Basil Rowe based on the data from the MPC NEO Confirmation page ([[http://www.minorplanetcenter.net/iau/NEO/toconfirm_tabular.html|NEOCP]]).
 +
 +This method allows you to plot the uncertainty map in CdC to help plan an imaging session to recover the asteroid. 
 +
 +Start by downloading the [[https://ap-i.net/pub/skychart/neo/NEO-CdC_plot_project.zip|project files]].
 +
 +Extract the zip file and read the documents __Uncertainty Map Plotting in Cartes du Ciel__ and  __How to Use for Excel or OpenOffice__.\\
 +
 +The process involves doing a copy/paste of the variant orbital elements from the NEOCP into a spreadsheet, then
 +using a macro to reformat the elements for use in CdC. 
 +
 +After that you can show the uncertainty map in CdC:
 +{{:en:documentation:neo-uncertainty.png?500|}}
 +
 +Please direct questions and comments to Basil Rowe (email address in project files)
  
en/documentation/display_of_neos.1360535289.txt.gz · Last modified: 2015/11/06 20:34 (external edit)