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  * Sentry

Sentry: Earth Impact Monitoring

    Introduction
    Object Table
    VI Table
    FAQ
    Operational Notes
    Removed Objects
    Object Details

Object Details

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The following summary tables includes basic information about the
hazard for this object. The maximum Torino and Palermo Scale values
are listed, as well as the number of tabulated potential impacts and
their corresponding cumulative Palermo Scale value and cumulative
impact probability (shown in the the first table). Certain parameter
values depend upon the specific impact event in question, but they
change little among the various table entries. For this reason we
tabulate only mean values for these parameters (shown in the second
table). The observation set used for the analysis is also listed.

[[ objSummary.fullname ]] -- Earth Impact Risk Summary (orbit details
)

    Torino Scale (maximum)      [[objSummary.ts_max]]
    Palermo Scale (maximum)     [[objSummary.ps_max | number:2 ]]  V[impact]  [[objSummary.v_imp | number:2 ]] km/s
  Palermo Scale (cumulative)    [[objSummary.ps_cum | number:2 ]] V[infinity] [[objSummary.v_inf | number:2 ]] km/s
Impact Probability (cumulative)                                        H      [[objSummary.h | number:1 ]]
  Number of Potential Impacts   [[objSummary.n_imp]]               Diameter   [[objSummary.diameter | number:3 ]] km
    Impact Search Technique     [[objSummary.method]]                Mass     [[objSummary.mass | exponentialFormat ]] kg
                                                                    Energy    [[objSummary.energy | exponentialFormat ]] Mt
Analysis based on [[ objSummary.nobs ]] observations spanning [[  All above are mean values
objSummary.darc ]]                                                weighted by impact probability
([[ objSummary.first_obs ]] to [[ objSummary.last_obs ]])

                 Impact Table (these results were computed on [[objSummary.cdate]])
                Sigma Sigma                   Sigma  Sigma Stretch    Impact    Impact Palermo Torino
     Date        VI    MC   Distance  Width   Impact  LOV    LOV    Probability Energy  Scale  Scale
(yyyy-mm-dd.dd)                (r       (r                    (r                 (Mt)             
                            [Earth]) [Earth])              [Earth])

Use the "Print" button above to print data contained in this table.
Use the "CSV" or "Excel" buttons to download the data for use in your
spreadsheet program. Allow a few seconds for downloads of large
datasets.

Machine-readable data are available. See the API document for
details.
Table Column Descriptions  |  [[legendButtonText]]   

Coloration
    The color of the table row gives a rough interpretation of the
    severity of the threat. White or gray colors indicate a Torino
    scale of 0 or undefined. All other colors (green, yellow, orange,
    and red) represent their respective Torino scale.
Date (yyyy-mm-dd.dd)
    Calendar date (UTC) of the potential impact.
Sigma VI
    Sigma VI is a metric that quantifies how well the impacting orbit
    found by the orbit-determination filter fits the observations.
    Zero indicates the best-fitting, central (nominal) orbit and the
    further from zero, the less likely the event: For an orbit
    defined by six orbital parameters, roughly 83% of the uncertainty
    region is within 3-sigma.
Sigma MC
    Sigma MC is a metric that quantifies how well the impacting orbit
    fits the observations. Zero indicates the best-fitting, central
    (nominal) orbit and the further from zero, the less likely the
    event: For an orbit defined by six orbital parameters, roughly
    83% of the uncertainty region is within 3-sigma.
Distance (r[Earth])
    Minimum distance on the target plane (scaled b-plane) from the
    LOV to the geocenter, measured in Earth radii. For these purposes
    the radius of the Earth, 6420 km, includes some allowance for the
    thickness of the atmosphere.
Width (r[Earth])
    One-sigma semi-width of the LOV uncertainty region, measured in
    Earth radii.
Sigma Impact
    Lateral distance in sigmas from the LOV to the Earth's
    atmosphere. Zero indicates that the LOV intersects the Earth. It
    is computed from (Distance - 1)/Width.
Sigma LOV
    Coordinate along the Line Of Variations (LOV). This value is a
    measure of how well the impacting orbit fits the available
    observations. Zero indicates the best-fitting, central (nominal)
    orbit and the further from zero, the less likely the event:
    Roughly 99% of all the uncertainty region lies between -3 and +3.
    Sentry explores out to Sigma LOV = +/-5.
Stretch LOV (r[Earth])
    Stretching is the semimajor axis of the local linear uncertainty
    region. It describes how fast one moves across the target plane
    as Sigma LOV changes, and is measured in Earth radii per sigma.
    The local probability density varies inversely with the
    stretching, and thus larger stretching values will generally lead
    to lower impact probabilities.
Impact Probability
    Probability that the tabulated impact will occur. The probability
    computation is complex and depends on a number of assumptions
    that are difficult to verify. For these reasons the stated
    probability can easily be inaccurate by a factor of a few, and
    occasionally by a factor of ten or more.
Impact Energy (Mt)
    Kinetic energy at impact, based upon the computed absolute
    magnitude and impact velocity for the particular case, and
    computed in accordance with the guidelines stated for the Palermo
    Technical Scale. Uncertainty in this value is dominated by mass
    uncertainty and the stated value will generally be good to within
    a factor of three.
Palermo Scale
    Hazard rating according to the Palermo technical impact hazard
    scale, based on the tabulated impact date, impact probability and
    impact energy.
Torino Scale
    Hazard rating according to the Torino impact hazard scale, based
    on the tabulated impact probability and impact energy. The Torino
    scale is defined only for potential impacts less than 100 years
    in the future.

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