NEO Planner V5.0 - Object Selection - Explanations
Within the picture, click on the zone that you want to be explained: (not in all browsers available)
Copyright: The data comes from official access to web services from MPC or the new API Web Service of the Horizons system of the JPL.
These settings are the third step in getting NEO Planner up and running.
Here you define the
Object Selection of NEO Planner.
In preparation for an observation session, so far you manually
spend some of the time picking out the observable objects and weighing which
objects are really suitable.
With the help of the settings made here, the objects are preselected analogous
to the manual entries on the MPC homepage and the ephemeris are determined.
NEO Planner only selects non-numbered NEOs and all observable comets.
When loading or saving Object Selection, the associated
current result of the
CGI-query at the MPC is displayed
due to the preset settings on the right in the window.
Plausibility checks or actions are usually only carried out after leaving the cursor in the input field.
The active observatory is displayed
- Ephemeris selection: NEO and Comets:
The result of the calculation of the
observation night is completely dependent on good parameters.
Neo Planner needs the ephemeris of each object over the entire period of the
coming night if possible.
This means that the number of ephemeris and the interval in minutes must be
coordinated in such a way
that there are enough ephemeris for each object in order
to calculate the optimal observation slot for position
and time.
The MPC returns the ephemeris related to the Observatory Code.
This means that the local altitude of the objects is included in the output.
Reaching the highest altitude is exactly the calculation goal for the best
observation time.
A well-functioning combination of the number
of ephemeris and the interval in minutes is number 40 and interval 20.
These suggested values should be
used to ensure that the entire observation period of the coming night is taken
into account.
In the months around Summer solstice in higher
latitudes around 45 degrees the number can also be set
to around 30 to prevent an overflow to the following day.
Interval in minutes per object:
Please look at the previous explanation.
The time intervals of the
ephemeris in these settings are only required for preselecting the objects
and play no role in the final calculation of the
observation ephemeris.
These are then determined to the minute, regardless of these settings.
Select objects from NEAM00.txt:
The determination of the
observable NEO per observatory code is no longer carried out via the
NEAm00.txt
of the MPC,
but via
the new
API Web Service of the
Horizons system
of the JPL.
This significantly reduces the loading time of the NEO's ephemeris, which
is good for the overall performance of the Execute process.
The loading of the observable NEO of the coming night is now carried out
according to the parameters defined by NEO Planner
such as minimum altitude or
limitation of magnitude.
Only those NEOs are taken into account whose last observation date is no longer
than the specified days ago.
A period longer than one year makes sense if you also want to carry out recovery
observations.
All NEO with V = xx.xx to xx.x:
The selection of the NEO can be narrowed down. It is possible to choose the brightness from ... to.
As a rule, every NEO observer has experience with the maximum NEO observable for
him in relation to their brightness and
should therefore enter his personal
experience value here.
NEO Planner will therefore only select those objects whose Vmag values are
numerically below the settings value.
The apparent speed does not play a role at this point
when considering the maximum usable brightness.
The following model is used to select the NEO:
First it is checked whether the Vmag of the ephemeris is maximum 0.4 mag weaker than the limit value in the settings. If so, the object will continue to be considered.
Second, if the apparent speed in the ephemeris is less
than 100.00 s / min, the average Vmag of the last 10 observations is used for
the selection of the object,
otherwise the Vmag of the ephemeris.
The reason for taking into account the apparent speed at the time of the
ephemeris is a possible strong
change in the Vmag compared to previous observations..
At speeds over 100 seconds / minute at the time of the ephemeris
we always use MPC's
designated Vmag of the ephemeris for selection.
Otherwise fast objects might not be taken into account.
In additon, during the calculation of the exposure times,
the selected NEO are subjected to a special Vmag
consideration.
See the explanations for the
revise button in the Preparation / Execute Planning tab
Minimum s/min x.xx: All objects, also NEOCP
Depending on the observation strategy, objects
that move below a defined speed per minute can be sorted out: s / min = arc
seconds per minute.
Extremely low speeds increase the number of images required for a measurement,
even with bright objects.
Each individual measurement should be made at the distance of the FWHW value.
Maximum s/min xxxx.xx: All objects, also NEOCP
Depending on the observation strategy, objects moving above a defined speed per minute can be sorted out: s / min = arc seconds per minute.
Sort out previously observed objects:
Mark the checkbox if previous own observations of objects
are to be taken into account when planning the object selection
and enter the number of days in the past within which the objects are not
selected until the current date.
- Ephemeris selection: Comets:
Select Comets with V = xx.xx to xx.x:
The selection of the comets can be narrowed down. It is possible to choose the brightness from ... to.
With comets, compared to NEO, you have to apply slightly different standards
with regard to the Vmag selection. Since comets usually appear spotty on the CCD
image,
the maximum usable brightness should be set somewhat brighter than with NEO. In
addition, comets move at far greater distances from the Earth,
which largely excludes a significant change in measured brightness.
29P SCHWASSMANN/WACHMANN with its regularly occurring
outbursts in brightness is certainly an exception here just like
outbreaks in other comets,
but is generally not taken into account.
The real brightness of comets is actually often very different from the
brightness we find in the ephemeris of the MPC.
Therefore to calculate the exposure
times, NEO Planner always uses the average Vmag of the last 10 observations,
which are computed from the last publishing by the MPC
with MPEC XXX: OBSERVATIONS AND ORBITS OF COMETS
AND A / OBJECTS.
Last observations since xx months:
Comets can lose their brightness very quickly,
which means that they have not been observed lately.
It is therefore advisable to include only those comets in the planning that have
been observed by observatories for a month.
However, if you intend to rediscover one in the coming orbit, you should increase
the value here accordingly.
NEOCP settings and some additional explanations:
Most of the following
settings represent a simulation of the manual entries on the NEOCP, which NEO
Planner automatically determines using so-called CGI queries.
Both the MPC and
JPL CNEOS Scout kindly offer such queries to motivated programmers.
The MPC delivers CGI results
in text format, while Scout sends so-called
JSON files, which
all have to be
parsed after receipt.
However, the Scout JSON queries are not used in the object selection at this
point, only NEOCP
objects are selected.
NEO Planner only uses the
Scout JSON queries when calculating the observation positions to the minute
during the calculation process,
which in contrast to the manual entries on the Scout website
do not have to endure long waiting times.
(The reason for the long manual waiting times of ephermeris calculated with
Scout, which every NEOCP observer knows, is, by the way,
the compulsory calculation of more than 1000 different orbital elements for each object.
NEO Planner, on the other hand,
makes a quick Scout query request only with the first 30
orbits, which experience shows is sufficient for planning.)
- Ephemeris selection: NEOCP:
Not seen less than xx.xxx days::
Newly discovered objects usually show only a few observations.
Most of the
objects listed on the NEOCP are too weak in terms of brightness or lie outside
the observable range.
To make matters worse, many objects were observed more than a day ago, which
makes it very difficult to find them again.
In the latter cases, the positions calculated by the MPC or JPL Scout can be
very far from the real position.
Therefore, especially
with the smaller field sizes of the CCD chip and longer focal lengths,
you should only target those objects that were observed no longer than a day
ago.
This is of course only a recommendation and depends on the motivation and
equipment of the observer.
Around the time of the full moon, it can make
sense to include objects with the last observation time in the past, especially
if several observations were made earlier.
All NEOCP object with V = -30 to xx.x:
Confirming NEOCP objects is both a motivation and a challenge. Experience has
shown that observers pay special attention to these objects.
The confirmation of new objects, but also the follow-up observation, is
important in order to allow as many measurements as possible to flow into
the
calculation of the orbital elements for a retrieval in later orbits.
with Declination between +/-xx and +/-xx:
Entering the observable area
in declination applies equally to NEOCP objects, NEO and Comets.
Enter exactly
the values that you would enter on the NEOCP.
Enter values between -90 and approx. +30 in the southern hemisphere!
with a NEO disirability score of xxx% and xxx%:
Usually from 0 to 100%
Entering interval 1 (30 minutes) usually ensures the required range of ephemeris over the entire night.
The NEOCP query results are displayed when the window is loaded based on the
parameters set.
In addition, the display adapts itself when you press the Save
settings button
based on the settings made.
JPL Scout n-orbits 1 to 30 xx:
The
Scout
offered by JPL
cneos shows the average
(median) determined ephemeris of the NEOCP object
against the background of a
high number (>1000)
of possible orbits and a correspondingly long calculation time.
Everyone knows this performance effect when using the Scout.
This very high-performance method provides the best positions of a newly
discovered object and is therefore preferred by the NEO
Planner.
However, NEO Planner does not calculate the ephemeris of NEOCP objects
completely and controls the median result in the API call
using a freely selectable number of orbits between 1 and 30.
Experience has shown that the median of 30 orbits is sufficient for objects with
arcs >= 8 hours,
to get a good
positioning very close to the online Scout ephemeris.
As a result, determination of the ephemeris by the Scout API is reduced to
around 4 seconds for these objects.
With arcs < 8 hours, NEO Planner uses an automated scaling of
the orbits to be calculated.
The number of orbits given here is increased by a factor of 2 to 8 per arc hour
approaching from 8 to 1.
This means that an arc of 7.xx hours n-orbits is increased by a factor of 2 =
60 n-orbits.
An arc of 4.xx hours increases the factor by 5 = 150 n-orbits, an arc of 1.xx
hours increases the factor to 8 = 240 n-orbits.
Arcs of less than 1 hour, which often consist of individual detection
measurements from an observatory, are treated as follows:
An arc between 0.5 and 0.99 hours increases the factor by 9 = 270 n-orbits, an
arc < 0.5 hours increases the factor to 10 = 300 n-orbits.
For an object with an arc < 0.5 hours, reading out the ephemeris with Scout-API
takes about 30 seconds.
You can choose the number of n-orbits as a basis for the median
calculation of the Scout itself between 1 and 30. 30 is recommended.
With the checkbox you can choose whether NEO Planner should perform the scaling
as just described or not.
So what does this mean for the accuracy of the NEOCP ephemeris in the NEO Planner?
The larger the arc of an object, the more precise positions are
displayed.
The shorter the arc of an object, the longer the planning takes.
Objects with a very short arc should be observed with caution, especially if
confirmatory measurements have not yet been submitted.
Suggestion for the planning method:
When planning for the first time, the setting should be: n-orbits = 30, no scaling.
Selecting a scaling makes sense in the following scenario:
After planning, you find objects with short arcs in the Revise and want to find
and confirm them.
Then you adjust n-orbits to e.g. 15 and click on scaling.
Re-planning will then
determine the positions of the short-track objects closer to the online scout
than without scaling.
If you are willing to accept a longer planning time, you can use the time-consuming online Scout method if the arc of the object is less than or equal to 2 hours:
The ephemeris in Scout for NEOCP objects can also be determined via the <all
objects...> checkbox in the default setting of Scout.
Orbits of objects with an arc of 2 hours or less are then
taken into account in the calculation in Scout.
The ephemeris determined in the planning then correspond to the values in the
online display on the Scout page.
However, if there are several short NEOCP objects in the planning,
this setting can lead to a considerable delay in Execute Planning or Smart
Planning in Rivise.
Experience has shown that planning NEOCP ephemerides using the original NEO
Planner method is generally sufficient.
From experience, Scout often calculates deviations of several minutes of arc or
even degrees of arc for very short orbits of fast NEOs
or even new slow comets, which is
why setting this checkmark does not play a major role in these cases.
However, to meet the highest reasonable NEOCP planning
requirements, check this box.