<StarIssues>Reliability|Gaia Duplicated Source flag|No Proper Motion flag|Proper
motion using UCAC4|Double star solution - star brightness
ratio|Uncertainty in the star brightness ratio, in percent|Double star solution RA offset (mas)| Double star solution Dec offset (mas)|Standard Deviation RA offset (mas)| Standard Devaition Dec offset (mas)</StarIssues>
<Asteroid> Number| Name| dX| dY| d2X| d2Y d3X| d3Y| Parallax| dParallax|
Nominal mean diameter (km)|Uncertainty in mean diameter (km)| Mv</Asteroid>
<EventFits>
<SolveFlags>X| Y| Major Axis| Minor Axis| PA Major Axis| Circular solution| Include Miss events|
Separation of 2nd star/asteroid moon| PA of 2nd star/asteroid moon</SolveFlags>
<EllipticFit>X| Y| Major axis| Minor Axis| PA Major Axis| Fit quality| Used
Assumed Diameter| Flag for future review|Center of Mass X| Center of Mass Y</EllipticFit>
<EllipseUncertainty>Sdev_X| Sdev_Y| SdevMajor| SdevMinor| SdevPA</EllipseUncertainty>
<ShapeModelFit>
<Fit>Source| ID| SurfaceDia/VolumeDia ratio| Fit quality| Phase correction| Volume Dia Min| Volume Dia Max|
Version</Fit>
.....
</ShapeModelFit>
<SatelliteFit>
<Satellite>IAU designation|SatdX|SatdY|Satd2X|Satd2Y|Separation|J2000 Position Angle|Uncertainty
in separation|Uncertainty in Position angle| Major axis| Minor Axis| PA Major Axis|
Fit quality</Satellite>
....
</SatelliteFit>
<DoubleStar>
<JDSO>Date of submission to the JDSO| JDSO publication reference </JDSO>
<Solution>PA| Separation| sdev_PA| Sdev_Separation| Centre_X| Centre_Y| Offset_X| Offset_Y|
Solution number</Solution>
...{either 1| 2 or 4 lines| depending on the nature of the solution}
</DoubleStar>
</EventFits>
<Astrometry>
<ReferenceTime>year| month| day|Reference hour|Uncertainty|AcrossPathUncertainty</ReferenceTime>
<MainBody>IAU designation|GeocentricX| GeocentricY|dRACosDec|dDec|UncertRA|UncertDec|
Position centered on shape model|number of chords used|Position for an unseen
primary of a binary asteroid|Fit code|Adustment to the across path
uncertainty|adjustment to the along path uncertainty|Maximum +'ve Hit chord
distance|Maximum -'ve chord distance|Minimum +'ve Miss chord distance|Minimum -'ve
chord distance</MainBody>
<MainAtConjunction>IAU designation|GeocentricX at conjunction|GeocentricY at
conjunction|Position for an unseen primary of a binary asteroid</MainAtConjunction>
<SatelliteBodies>
<Secondary>IAU designation|GeocentricX| GeocentricY|PA_2000|dRACosDec|dDec|UncertRA|UncertDec|number
of chords used</Secondary>
<SecondaryAtConjunction>IAU designation|MiriadeMotions|GeocentricX| GeocentricY|Year|Month|
Day of
conjunction|Sdev_day|Sdev_AlongTrack|Separation|Sdev_Separation|PAatConjuncton</SecondaryAtConjunction>
...}
...}
</SatelliteBodies>
<MPC>Date of publication|Circular number|MPC Submission ID</MPC>
</Astrometry>
</Details>
<Observations>
<Prediction>Seq Num|Longitude| Latitude| hr| min| sec|Event comments</Prediction>
<Observer>
<ID>Seq Num| Observer1| Observer2| MoreThan2Observers| NearLocation|
State/country| Longitude| Latitude| Alt| Datum| TelescopeAperture| TelescopeType| Observing method| Time Source</ID>
<Conditions>Stability| Transparency| SN| Time Adjustment| Comment</Conditions>
<D>hh mm ss.ss| eventCode| Accuracy| PEqn| Weight| PlotCode</D>
<R>hh mm ss.ss| eventCode| Accuracy| PEqn| Weight| PlotCode</R>
</Observer>
...
</Observations>
<Added> yyyy|m|d</Added>
<LastEdited>yyyy|m|d</LastEdited>
</Event>
</Observations>
The tag <FileVersion> specifies a version number for the file format. The
number is a decimal number, and is used to identify the need to upgrade either
the file, or the version of Occult.
The tag <Event> delimits the data for an event. The whole file will be read
into memory, but only data within an event will be decoded (when required).
Within an event, the tags <ShapeModelFit>, <DoubleStar> and <BinaryAsteroid>
will only be present when appropriate, as will three items under <Astrometry>
Within a data element, individual items are stored as pipe-separated-values.
This allows commas to be used in several fields.
| Tag |
Data items |
| Date |
Date of the event
- The year, month, and day of the
event, and the hour (to 0.1 hrs) close to the observed event times. If
observations extend across different days, specify the earlier day,
with times going above 24hrs as required.
|
| Star |
Details of the star
- Catalogue - the
catalogue identifier. The identifiers used are:
HIP
(Hipparcos), Tycho2 (or TYC), UCAC4, USNO-B1, NOMAD and G-coords
- Number - the number in the catalogue
- Gaia version - The source of the star position. 0 = Hipparcos2,
1 = Gaia DR1, 2 = Gaia DR2, 3 = Gaia EDR3, 9 = USNO Bright Star
Catalogue (UBSC, 2022), -1 = not specified
- Gaia id - the 18-digit Gaia id in the relevant Gaia version
- Right Ascension (hh.hhhhhhhhhh - the RA of the star. GCRS
coordinates. (That is, coordinates referred to the ICRS reference
frame of 2000, proper motion to date, corrected for parallax). No correction
for relativistic light bending.
- Declination (ħdd.ddddddddd) - the Declination of the star, GCRS
coordinates. No correction
for relativistic light bending.
- Uncertainty in Right Ascension (mas) - incorporating
position, proper motion and parallax uncertainties
- Uncertainty in Declination (mas) - incorporating position,
proper motion and parallax uncertainties
- Angular diameter of star (mas) - using the Gaia estimated
star diameter from DR2. For stars
added after the beginning of 2021, an estimate based on the
stars magnitudes is given as the quantity is not available in
EDR3.
- Issues flag. 0 = no issues, 1 = high RUWE, 2 =
Duplicate source flag, 3 = 1 + 2.
- see Notes for
explanations
- Right Ascension - apparent, hh.hhhhhhhh. The apparent RA of
the star at the Date+time of the event, with no correction for relativistic light bending.
- Declination - apparent (ħdd.ddddddd) The apparent
declination of the star at the Date+time of the event, with no correction for relativistic
light bending.
- Mb - The Gaia blue magnitude of the star
- Mg - The Gaia G magnitude. For non-Gaia stars, the V magnitude
- Mr - The Gaia red magnitude of the star. Where available, the Red
Photometer magnitude of Gaia
- EPIC ID - the identification of stars if they are
observed in the Keplar2 mission
|
| StarIssues |
Extra details about the star
- Reliability. A measure of whether the star position is fully
reliable.
- For Gaia stars, the value is the RUWE (Renormalised Unit
Weight Error). "The
RUWE is expected to be around 1.0 for sources where the
single-star model provides a good fit to the astrometric
observations. A value significantly greater than 1.0 (say,
>1.4) could indicate that the source is non-single or
otherwise problematic for the astrometric solution."
- For star positions sourced from TychoGaia: the
'astrometric-excess-noise' parameter
- For star positions sourced from Hipparcos2: a value
computed using the Hipparcos values of Ntr, F2, and the
number of parameters in the solution. The result is largely
equivalent to RUWE.
- Duplicated Source flag. A flag in Gaia. 0 = not set, 1 = set,
-1 = not specified (that is, position comes from TychoGaia or
Hipparcos2)
During data processing, this source happened to be duplicated and only one source identifier has been kept. Observations assigned to the discarded source identifier(s) were not used. This may indicate observational, cross-matching or processing problems, or stellar multiplicity, and probable astrometric or photometric problems in all cases. In Gaia DR1 and DR2, for close doubles with separations below some 2 arcsec, truncated windows have not been processed, neither in astrometry nor photometry. The transmitted window is centred on the brighter part of the acquired window, so the brighter component has a better chance to be selected, even when processing the fainter transit. If more than two images are contained in a window, the result of the image parameter determination is unpredictable in the sense that it might refer to either (or neither) image, and no consistency is assured.
- No proper motion flag. Indicates that no proper motion
has been specified in the Gaia catalogue. Values are 0 = has
proper motion, 1 = no proper motion, -1 = not specified (that
is, position comes from TychoGaia or Hipparcos2, which will have
proper motions). An RUWE of 0 appears to be applied when there
is no proper motion in Gaia.
- Proper motion derived using UCAC4. For some stars where
there is no proper motion in Gaia, and approximate proper motion
was added by comparing the UCAC4 J2000 position with the Gaia
2016 position. Values are 0 = (includes stars with Gaia proper
motions, or stars with no Gaia proper motions that were not
matched to UCAC4), 1 = proper motion added, -1 = not
specified (that is, the position comes from TychoGaia or
Hipparcos2)
- Double star - ratio of star brightness. Default is 1.2. The
ratio is used to determine to location of the Gaia position
along the component separation. If R is the ratio
(reference/other), the distance of the reference star from the
Gaia position is Separation/(R + 1)
- Uncertainty in the star brightness ratio, as %. Default is
10
- Double star solution, offset in RA. The offset in RA from
the Gaia position, of the component used for the occultation
solution.
- Double star solution, offset in Dec. The offset in Dec from
the Gaia position, of the component used for the occultation
solution.
- Double star solution, Standard deviation in offset in RA.
- Double star solution, Standard deviation in offset in Dec.
|
| Asteroid |
Details of the asteroid
- Number - the number of the asteroid
- Name - the asteroid's name, or other identification [the
name of asteroid (229762) G!kun||'homdima is held as
Gunhoumdima]
Positions on the Apparent fundamental plane are computed using
orbital elements at the Date + time of the event, with the
shadow motion being expressed as
a*T + b*T2
+ c*T3 ,
where T is the time (in hours) from the hour under Date.
The following give the coefficients for this expression.
- dX - coefficient 'a' in X (Earth radii/hr)
- dY - coefficient 'a' in Y (Earth radii//hr)
- d2X - coefficient 'b' in X (Earth radii/hr2)
- d2Y - coefficient 'b' in Y (Earth radii/hr2)
- d3X - coefficient 'c' in X (Earth radii/hr3)
- d3Y - coefficient 'c' in Y (Earth radii/hr3)
- Parallax - in arcsec, at the hour under Date
- dParallax - in arcsec. The hourly rate of change in parallax
- Nominal mean diameter - in km. Typically from IR satellite
measurements
- Uncertainty in that diameter - km (added in v2.2)
- Mv - the Visual magnitude of the asteroid
|
| SolveFlags |
Flags for automatic fitting
A number of
parameters can be set for automatic fitting - and this is indicated
by a flag. The flag is:- 0
if the parameter has not been included in
the automatic fitting
- 1 if the parameter was
included in the automatic fitting of an ellipse to observed chords
The parameters for which the flags are set
are:
- X coordinate
- Y coordinate
- Major Axis
- Minor Axis
- PA Major Axis
- Circular solution
- Include Miss events
- Separation of 2nd star/asteroid moon
- PA of 2nd star/asteroid moon
|
| EllipticFit |
Details of the fit of an ellipse to the
observed chords
- X - X-coordinate of the center of
the best-fit ellipse (in km) relative to the reference frame used to
plot the observations
- Y - Y-coordinate of the center of the best-fit ellipse (in km)
relative to the reference frame used to plot the observations
- Major axis - in km
- Minor Axis - in km
- PA Major Axis - in deg
- Fit quality - a code indicating the quality of the fit
0 = 'No reliable position or size'
1= 'Astrometry
only. No reliable size' Observation can
be used to report astrometry, but nothing meaningful about the
asteroid's size.
2 = 'Limits on size, but no shape'. Poor coverage around the profile, but
a diameter is determinable (often with a fit to a shape model)
3 = 'Reliable size. Can fit to shape models'. Good coverage around much of the profile enabling a reliable
determination of the asteroid's size - even without a shape model
4 = 'Resolution better than shape models'. Profile of the asteroid well covered with highly
consistent results
5 = 'Short duration event. No astrometry'. For
events where there is only one positive chord, and the duration of the
potential occultation is for one or two video frames or camera exposures. Such
events are not used for any reporting process; it is provided only as a
holding place.
6 = 'Only 1* of a double. No astrometry'. For events where the
observed light drop was clearly less than the expected drop, and
could not be explained by variation in the brightness of the
asteroid - leaving the only explanation being the occultation was
one component of a double star, with the other component not
detected. No astrometry because the location of the photocenter to
match the Gaia star position cannot be determined.
- Used Assumed Diameter - flag to indicate the major/minor axes
are assumed values (e.g. from IR satellite measures) rather than
derived from the observation.
- Flag to indicate the event should be reviewed in the future
because of particular issues that might be resolved with further
information (0 = false, 1 = true)
- X-offset from X to the Center of Mass location - in km
- Y-offset from Y to the Center of Mass location - in km
|
| EllipseUncertainty |
The standard deviations of the values for the fitted ellipse
- X - X-coordinate of the center of
the best-fit ellipse relative to the reference frame used to
plot the observations (km)
- Y - Y-coordinate of the center of the best-fit ellipse
relative to the reference frame used to plot the observations
(km)
- Major axis - in km
- Minor Axis - in km
- PA Major Axis - in deg
|
| ShapeModelFit |
Where shape models are available, this
group gives data about the fits to shape models
Each shape
model has its own group with the tags <Fit> </Fit>. The
items within each such group are:
- Source - The shape model source name (DAMIT, ISAM)
- ID - the identification within that source
- SurfaceDia/VolumeDia ratio - the ratio of the Surface-equivalent diameter
to the Volume-equivalent diameter of the shape model.
- Fit quality - a flag to indicate whether the model is consistent with
the occultation observations.
0 = Not fitted. Too few chords
to make a fit to the shape model.
1 = Bad occn data. The
occultation observations are either inconsistent or unreliable,
with no ready way of distinguishing between reliable and
unreliable observations
2 = Model wrong. The shape
model is clearly inconsistent with the observed
chords
3 = Minimum Dia. Usually associated with a single
chord observation, with that chord being matched to the largest
dimension of the shape model to give its minimum diameter
4 =
Diameter but no fit. The chords do not sensibly match the shape
model, yet it is possible to derive minimum and maximum possible
diameters. [NOTE: flag 1 - Model wrong - should be used unless
there is a degree of confidence that the derived diameters are
'in the right ball-park']
5
= Poor fit. The shape model is generally consistent with the
observed chords - but has some broad deviations
6 = Good fit.
The shape model has a high degree of correspondence with the
observed chords.
7 = Not constrained. The observations have
been compared to the shape model, but the distribution of the
chords, or the magnitude of the uncertainties, were such that no
meaningful constraints could be determined. Setting 7 added with
effect from May 2022
- Phase correction - the rotational correction (in degrees)
applied to optimize the fit. Only applied if the light curve
data warrants such an adjustment.
- Volume Dia Min - the minimum volume-equivalent diameter arising
from a fit of the chords to the shape model
- Volume Dia Max - the maximum volume-equivalent diameter arising from a fit of
the chords to the shape model
- Version - information about the version
|
| Satellite |
Details of an observed companion to an
asteroid
This group only appears if the
observation shows the presence of two bodies.
As
at 2019, the fit to the satellite is 'manual', so there
are no determined standard deviation values
- IAU designation of companion
- Sat_dRA - motion of the satellite in Right Ascension relative to the
system's center of mass. Units are mas/hr. The zero time is same as for the motions of
the main body. [Note this and the following three items are only
set if a Miriade ephemeris is available for the system.
Otherwise the values are set to zero. These values are only used
to align the chords of the satellite.]
- Sat_dDec - motion in Declination relative to the system's
center of mass
- Sat_d2RA - 2nd order motion in Right Ascension relative to the
system's center of mass
- Sat_d2Dec - 2nd order motion in Declination relative to the
system's center of mass
- Separation (mas)
- PA (deg) PA of companion with respect to the main body -
Apparent reference frame
- Uncertainty in Separation (mas)
- Uncertainty in PA
- Major axis (km) - of the companion
- Minor Axis (km) - of the companion
- PA Major Axis (Deg) - of the companion
- Fit quality
- None No fit to the satellite. This is
only used when the observations indicate the detection of a
satellite, but the observations have not been analyzed to
obtain a fit to the observations.
- Is it a satellite? The
observations indicates the possibility of a satellite.
However the observational evidence is not sufficient to
assert a definite detection. [Single-chord visual
observations would typically fall into this category, as
well as single noisy video recordings]
- Approx offset The existence
of a satellite is reasonably definite. The approximate location of
the satellite can be determined, but not its size or shape
- Offset + size An accurate location location
of the satellite is determined, together with a size
derived by assuming it is spherical
- Offset + shape An accurate determination of
the location, size and shape of the satellite.
- CBET number announcing the occultation discovery
|
| DoubleStar |
Details of double star solutions
This
group only appears if the observation indicates the star is double.
The number of times this line can appear depends on the
circumstances of the event, as follows:
1 - if there are two or more
spaced chords for both the primary and secondary star, such that there
is no doubt about which side of the asteroid the primary or secondary
star passed as seen by the observers. This provides a unique solution.
2 - if there are two or more spaced chords for one component of the
pair - such that there is no doubt about which side of the asteroid that
component passed. However if the other component does not have
sufficient chords to determine which side of the asteroid it passed,
there are two possible solutions.
4 - if the number of observed
chords is insufficient to locate either component against one or other
side of the asteroid, leading to 4 possible solutions. This situation
most commonly occurs with single-chord events, but it also occurs when
there are two or more chords which happen to be closely spaced such that
the relevant side of the asteroid cannot be determined.
| Tag |
Data items |
| JDSO |
Publication in Journal of Double Star Observations
- Date of submission to the JDSO
- JDSO publication reference - Volume/Issue/Page
|
| Solution |
The double star solution, or
one of multiple double star solutions.
This
group is repeated as often as required
- 1, 2 or 4 times.
- PA - the PA of the
companion (deg)
- Separation - the separation of the components (mas)
* may be negative: see note below
- Uncertainty in PA
- Uncertainty in Separation
- Centre in X - for when there are plural
solutions
- Centre in Y - for when there are plural
solutions
- Offset in X
- Offset in Y
- Solution number
The Offsets in X and Y apply when there are insufficient chords
to locate the primary star on one side or the other of the asteroid.
In this situation there are 4 potential solutions:
* primary star on one side of the asteroid, with secondary
on one or the other side; and
* primary star on other side of
asteroid, with secondary on one or the other side.
The offset value
places the primary star one one or other side of the
asteroid, avoiding the need to re-solve for the position of
the asteroid. The astrometric position is for the mean
relative location of the primary star.
Where the
occultation is of one star only of a double star
(demonstrated by the light drop being significantly less
than expected, the Separation is specified as a negative
value |
|
| Astrometry |
Details of the astrometric solution
derived from the event
This group only appears if the quality
setting under EllipticFit is greater than 0.
There are three groups under this
heading:
| Tag |
Data Items |
| ReferenceTime |
The time used for reporting
an event.
If the event involves a satellite,
this time is the average of all events involving the
satellite that have been used in the solution. This time is
used for both the satellite, and the primary body.
If
the star is a double star, only the primary events are used. The first step
in the solution is to identify the location of the center of the
asteroid relative to the geocenter, at a time identified by a
particular observed event that is used to define the plot axes.
-
Year (yyyy)
-
Month (mm)
-
Day (dd)
-
Reference hour (hh.hhhhhh)
-
Uncertainty in the reference time (s.sss) (including
effect of earth's rotation during uncertainty
period)
-
Across Path Uncertainty (mas) (arising from
earth's rotation during uncertainty period)
|
|
MainBody |
Event details at the Reference Time
- IAU
designation
- FundamentalPlaneX (km) kkkk.k (apparent)
- FundamentalPlaneY (km) kkkk.k (apparent)
- dRACosDec (arcsec) - J2000
- dDec (arcsec) - J2000
- UncertRA (arcsec) - uncertainty in Time
included. This data element is not used. Final RA
uncertainty is based on along/across track uncertainties
and time uncertainty.
- UncertDec (arcsec) - uncertainty in Time included.
This data element is not used. Final Dec uncertainty is
based on along/across track uncertainties and time
uncertainty.
- Position centered on shape model (0=false, 1=true).
Set to false if <EllipticFit>, X-offset or Y-Offset, are
non-zero
- number of chords used
- Position is for an unseen primary of a binary
asteroid
(0=false, 1=true), and is used solely as the
origin for the position of the satellite.
The values of dRACosDec
and dDec are 'observed' values. They have been converted
from the Apparent reference frame to J2000. They have not had the
effects of deflection of the asteroid relative to the
star removed.
- Fit code - uncertainty in position of center of asteroid.
Parts of the Error Code use the following 5 parameters, which relate to the distance of certain chords on either side of the center of the asteroid. In these parameters, the side of the path is indicated as Plus, or Minus - with Plus referring to the north-side of the path. Hit refers to positive occultation events, while Miss refers to Miss events. The Hit parameters specify the distance of the furthest positive chord on either side of the path, with a value of zero if there is no such chord on the particular side. The Miss parameters specify the distance of the closest Miss chord on either side of the path, with a value of +9 or -9 if there is no such chord on the particular side. The distances are expressed in units of the asteroid's assumed radius. :
Well-located : PlusHit >= 0.3 and MinusHit <= -0.3
Poorly-Located : (PlusHit - MinusHit) > 0.5, with either PlusHit < 0.3 or MinusHit > -0.3
Constrained : either PlusMiss < 1.3 or MinusMiss > -1.3
Unconstrained : none of the above
MeanLocation :the Absolute Value of the average of PlusHit and MinusHit - with the MeanLocation value limited to between +0.2 and +0.8.
The fit uncertainty categories are:
a - the uncertainty is that from a least squares fit of an unrestricted ellipse to the observed chords. This provides the minimal value of the uncertainties. (a) is usually replaced by one of the following codes. However it will appear for occultations by the major planets and larger planetary satellites, when they have a known diameter and are known to be spherical.
b -
For asteroids only. If the astrometric position is set to match the _center_ of a shape model (center of mass solution) - the uncertainties for both the
Along-Path and Across-Path directions are set at 5% of the assumed diameter.
c - if not b, but has a shape model fit of either 'poor' or 'good'
c1 - If the overall event quality is 'Reliable Size...' or 'Resolution better than Shape models': uncertainties for both the
Along-Path and Across-Path directions are set at 8% of the assumed diameter.
c2 - If the overall event quality is 'Limits on size, but no shape': uncertainties for both the
Along-Path and Across-Path directions are set at 12% of the assumed diameter.
(d) -
for major planets & their large moons. This relies on they being essentially circular in profile, and their diameters being accurately known - to provide good astrometry in circumstances which would not apply to asteroids.
d1 - if Well-located: uncertainties of (a), unchanged
d2 - if Poorly-located: three times the uncertainties of (a)
4% of assumed diameter
d3 - if Constrained:
(i) if only 1 chord, or the spread of the chords is less than 5% of the assumed diameter,- if the motion in the time uncertainty period is greater than the Along-Path uncertainty, that motion distance is taken as the Along-Path uncertainty. The Along-Path and Across-Path uncertainties are taken as this value.
- otherwise the Along-Path and Across-Path uncertainties are the uncertainties from the fit
(ii) if not (i), the Along-Path and Across-Path are the uncertainties from the fit.
** For both (i) and (ii): The Across-Path uncertainty is divided by the
MeanLocation value, and the
Along-path uncertainty is divided by SQRT(1- MeanLocation^2)
d4 - if Not-constrained:
(i) If only one chord, - the Along-Path uncertainty is computed on the same basis as for 'd3 - if Constrained', (i),
first dot point.
- if the chord is located more than 2 arc-seconds from the center of the object, the Across-Path uncertainty is computed on the same basis as for 'd3 - if Constrained', (i), first dot point.
- Otherwise the Across-Path uncertainty is set as 25% of the object's assumed diameter
(ii) If more than one chord- the Along-Path uncertainty is computed on the same basis as for 'd3 - if Constrained', (i),
second dot point.
- if the MeanLocation value is greater than 25% of its assumed radius, AND (PlusHit -
MinusHit) >0.05,
OR the MeanLocation value is greater than 15% of its assumed radius, AND (PlusHit -
MinusHit) >0.10,
the Across-Path uncertainty is the uncertainty from the fit - otherwise the Across-Path uncertainty is set as
25% of the object's assumed diameter
** For both (i) and (ii): The
Across-Path uncertainty from the first two dot points (but not the third) is divided by the
MeanLocation value. The
Along-path uncertainty is divided by SQRT(1- MeanLocation^2)
e - if (b), (c) and (d) do not apply:
This applies to events where quality is better than
'Astrometry only', and either (i) the Major + Minor axes are
included in the Least Squares solution, or (ii) the solution is for
a circle. The uncertainties are separately considered in the
Along-Path and Across-Path directions, and are set as the larger of the
uncertainty from (a), and the uncertainty specified in the relevant one
of e1 to e8:
If the overall event quality is 'Limits on size, but no shape'
e1 - Well-located - uncertainty must be at least 8% of assumed diameter
e2 - Poorly-located - uncertainty must be at least 12% of assumed diameter
e3 - Constrained - uncertainty must be at least 16% of assumed diameter
e4 - Unconstrained - uncertainty must be at least 20% of assumed diameter
If the overall event quality is 'Reliable size', or 'Resolution better than Shape models'
e5 - Well-located - uncertainty must be at least 5% of assumed diameter
e6 - Poorly-located -uncertainty must be at least 8% of assumed diameter
e7 - Constrained - uncertainty must be at least 12% of assumed diameter
e8 - Unconstrained - uncertainty must be at least 16% of assumed diameter
f - if none of (b) to (e) apply:
Across-Path
uncertainty set on following basis:
f1 - Well-located: the uncertainty in the assumed diameter of the asteroid.
f2 - Poorly-located: twice the uncertainty in the assumed diameter of the asteroid./span>
f3 - Constrained: twice the uncertainty in the assumed diameter of the asteroid (same as f2).
f4 - Unconstrained: 40% of the assumed diameter of the asteroid.
Along-Path uncertainty for each of f1 to
f4, is set on following basis:
For each positive chord::
- if chord length > 0.8 of assumed diameter - the Along-Path uncertainty for that chord is set at 5% of assumed diameter of the asteroid.
- else if chord length > 0.6 of assumed diameter - the Along-Path uncertainty for that chord is set at 10% of assumed diameter of the asteroid.
- Otherwise - the Along-Path uncertainty for that chord is set at 20% of assumed diameter of the asteroid.
Along-Path uncertainty set as the mean of the individual Along-Path uncertainties, assessed in inverse quadrature (to give greater significance to smaller uncertainty values).
- The increase from codes (b) to (f) to
the Across-Path uncertainty compared to
the uncertainty from (a) (km)
- The increase from codes (b) to (f) to the Along-Path uncertainty
compared to the uncertainty from (a) (km)
- Maximum +'ve Hit distance, asteroid radii d.dd (always set)
- Maximum -'ve Hit distance, asteroid radii -d.dd (always set)
- Minimum +'ve Miss distance, asteroid radii d.dd; 9 = not set
- Maximum -'ve Miss distance, asteroid radii -d.d; -9 = not set
|
| MainAt
Conjunction |
Event details at for the time of
Geocentric Conjunction
- IAU
designation
- GeocentricX at Conjunction (km) kkkk.k
- GeocentricY at Conjunction (km) kkkk.k
- Year of Conjunction
- Month of Conjunction
- Day of Conjunction dd.ddddddd
- Standard Deviation in Time of Conjunction d.ddddddd
- Standard deviation Along-track (mas) (s.s) -
from fit only, SDev in Time of Conj not included
- Separation at conjunction (arcsec) ss.ssss
- Standard deviation Across-track {Separation} (mas) (s.s)
- Position Angle of Conjunction (deg) ddd.ddd
- Position is for an unseen primary of a binary
asteroid
(0=false, 1=true), and is used solely as the
origin for the position of the satellite
The values are 'observed' values. They have been
converted from the Apparent reference frame to J2000. They
have not had the effects of deflection of the asteroid
relative to the star removed.
|
|
Secondary |
Event details at the Reference Time
- IAU
designation
- GeocentricX (km) kkkk.k
- GeocentricY (km) kkkk.k
- PA (deg) PA of companion with respect to the main body -
J2000 reference frame
- dRACosDec (arcsec)
- dDec (arcsec)
- UncertRA (arcsec)
- UncertDec (arcsec)
- number of chords used
The values of dRACosDec
and dDec are 'observed' values, They have been converted
from the Apparent reference frame to J2000. They have
not had the effects of deflection of the satellite relative to the
star removed.
|
| SecondaryAt
Conjunction |
Event details at for the time of
Geocentric Conjunction
- IAU
designation
- Satellite motions (from Miriade) allowed for in the
solution. 0 = no, 1 = yes
- GeocentricX at Conjunction (km) kkkk.k
- GeocentricY at Conjunction (km) kkkk.k
- Year of Conjunction
- Month of Conjunction
- Day of Conjunction dd.ddddddd
- Standard Deviation in Time of Conjunction d.ddddddd
- Standard deviation Along-track (mas) (s.s)
- Separation at conjunction (arcsec) ss.ssss
- Standard deviation Across-track {Separation} (mas) (s.s)
- Position Angle of Conjunction (deg) ddd.ddd
The values are 'observed' values. They have been
converted from the Apparent reference frame to J2000. They
have not had the effects of deflection of the asteroid
relative to the star removed.
|
| MPC |
Details of publication by the Minor Planet Center
- Date of submitting the accepted observation to
the MPC
- MPC Circular number of the summary report
- MPC Observation ID
|
|
| Observations |
This provides a series of groups giving
details for each observer
There are two groups under
this heading.
| Tag |
Data items |
| Prediction |
Details for a predicted central
line location near the observed locations
The
prediction information is used to validate the observed data,
and to calculate the offset between prediction and observed
- Sequential reference number
- Prediction Longitude (ħddd mm ss.s)
- Prediction Latitude (ħdd mm ss.s)
- Time (hh mm ss.s) The time is always positive. For events near 0hrs UT, the hour
can be 24 or more
- Event comments. A free-text field for overall
comments about the event - such as why no astrometry is
reported. Field added at start of 2021 - and is
incomplete for earlier years. From Nov 2021, field
includes the source of the orbit used for the prediction
in this tag.
|
| Observer |
Observer details.
This
group is repeated as often as required
There are
four groups under this heading.
| Tag |
Data Item |
| ID |
Details of the observer and
equipment
- Sequential reference number
- Name 1
- Name 2
- More Than 2 observers
- located near
- State or country (2 or 3 letter code)
- Longitude (ħddd mm ss.s)
- Latitude (ħdd mm ss.ss)
- Alt (m)
- Datum
_ = WGS84
N = NAD1927
E =
ED1950
T = Tokyo
G = GB1936
* =
unspecified, or other.
- Telescope Aperture (cm)
- Telescope Type
_ = unstated
1 =
Refractor
2 = Newtonian
3 = SCT
4 = Dobsonian
5 = Binoculars
6 = Other
7 = None
8 = Electronic [intended to refer to
small-aperture self-aligning telescopes with an
electronic detector]
- Observing method
unspecified
a Analogue & digital video
b Digital SLR-camera video
c
Photometer
d Sequential images
e
Drift scan
f Visual
g
Other
- Time Source
unspecified
a GPS
b NTP
c Telephone (fixed or mobile)
d Radio
time signal
e Internal clock of recorder
[such as by calibrating the recorder well before
and after the event]
f
Stopwatch
g
Other
|
| Conditions |
Observing Conditions
- Stability
_ = unstated
1 = Steady
2 = Slight flickering
3 = Strong flickering
- Transparency
_ = unstated
1 = Clear
2 = Fog
3 = Thin cloud <2 [mag loss <2 mag.]
4 = Thick cloud >2 [mag loss >2 mag.
5 =
Broken opaque cloud [that is, observed thru gaps
in the cloud]
6 = Star faint
7 = By
averted vision
- SN
- Time Adjustment (ħs.ss) [Adjustment to
time base of observer, to fit to other
observations ]
- Free-text comments
|
| D |
Details of the D event
- hh mm ss.ss. Always +'ve
values. For events near 0hrs UT, the hour can be 24h or more
- event Code
D for main star
d for 2nd
star
G for
satellite with main star
g for satellite
with 2nd star
M applies to situations where an occultation event could not be reliably detected. Most commonly this relates to a situation where the object did not occult the star. However there may be other explanations for the non-detection.
m applies to situations where an occultation event involving a 2nd star of a double star could not be reliably detected. Most commonly this relates to a situation where the object did not occult the 2nd star. However there may be other explanations for the non-detection.
N for events
involving a ring. The D and R times are for opposite arms of a ring. Where there is a D+R for an arm of a ring, the mid-time is specified, with the duration being given in FREE_TEXT
n for asteroids (or planets) known to have one or more rings, and an occultation by that ring(s) could not be reliably detected. Most commonly this relates to the star not crossing the orbit of any ring, or the absence of material in the portion of a ring crossed by the star. However there may be other explanations for the non-detection.
C for Not Seen -
e.g. because of cloud
e for an artificial D time
of the primary body of an asteroid with
satellites - for use when the primary component
is not observed. Always a predicted location
and time.
- Accuracy (s.ss) [usually specified by the observer. See below for default values when not specified.]
- PEqn (s.s)
- Weight [Usually
set as 'blank'. See below for default values
that are then applied]
- Include in Solution Code
_ Include observation
x Exclude observation
y Include D only
z Include R only
|
| R |
Details of the R event
- hh mm ss.ss. Always +'ve values. For
events near 0hrs UT, the hour can be 24h or more
- event Code
R for main star
r for 2nd
star
B for
satellite with main star
b for
satellite with 2nd star
M applies to situations where an occultation event could not be reliably detected. Most commonly this relates to a situation where the object did not occult the star. However there may be other explanations for the non-detection.
m applies to situations where an occultation event involving a 2nd star of a double star could not be reliably detected. Most commonly this relates to a situation where the object did not occult the 2nd star. However there may be other explanations for the non-detection.
N for events
involving a ring. The D and R times are for opposite arms of a ring. Where there is a D+R for an arm of a ring, the mid-time is specified, with the duration being given in FREE_TEXT
n for asteroids (or planets) known to have one or more rings, and an occultation by that ring(s) could not be reliably detected. Most commonly this relates to the star not crossing the orbit of any ring, or the absence of material in the portion of a ring crossed by the star. However there may be other explanations for the non-detection.
C for Not Seen -
e.g. because of cloud.
f for an artificial R time
of the primary body of an asteroid with
satellites - for use when the primary component is not observed. Usually a predicted location and time.
- Accuracy (s.ss)
[usually specified by the observer. See below for default values when not specified.]
- PEqn (s.s)
- Weight [Usually set as blank. See below for default values that are then
applied.]
- Include in Solution Code.
_ Include observation
x Exclude observation
y Include D only
z Include R only
|
| LightData |
Meta data for the light curve of the observation
When the event is soon after 0hrs UT, the start of
the light curve can be in the day preceding the date in
the Date field above. Similarly, if the event time is
greater than 24h, the start of the light curve can be in
the day following the date in the Date field above.
- Year - for first data point
- Month - for first data point
- Day - for first data point
- Hr - for first data point
- Min - for first data point
- Sec - for first data point
- Duration - the time difference in seconds between
the first and last data points in the light curve
- #Points - the number of data points in the light curve
|
| LightValues |
Light Curve values, as integers
- A series of values representing the light
curve value.
The values are scaled such that the maximum value is set to 9524 (=10,000/1.05). As a result, all light curve values have a maximum near to, but less than, 10000 - irrespective of the numeric values in the source light curve. (No adjustments to the zero-level in the light curve data are applied.)
Where the light curve is missing one or more exposures, the data element for that exposure is empty.
The number of elements is specified in
#Points in LightData
|
Some items have default values:
Accuracy is usually set by the observer. However when not set (which most commonly occurs for observations before 2000) the accuracy is set as follows:
- If the observing Method was 'a', 'b', or 'c'
- 0.5 sec if the Time Source was 'a', 'd', 'e', 'f'
;
- 1.5 sec if the time source was 'b', 'c', or 'g'
- 1.0 sec if the observing Method was 'd', 'e', 'f', or 'g'
Weight is usually
set as Blank. When solving for the best fit, the applied weights
are:
5 - for analogue or digital (non-SLR) video
4
- for digital SLR-camera
video, and Photometer
3 - for sequential images and drift scan
1 -
for visual and anything else.
0 - event is ignored in any
solution, but may still be plotted
Miss events are
considered only if expressly included in the solution - in which
case they are weighted 5.
Plot code - determines
whether an event is plotted in Occult, and by corollary whether
the event is reliable in any way. The settings are:
<blank> -
both events plotted
x - neither event is plotted
y - only
the D event plotted
z - only the R event plotted
|
|
| Added |
The date the record was
added to the file |
LastEdited |
The date the record was
last edited |