SOCRATES Format Documentation

This documentation describes the CSV format used for the SOCRATES results from each run, which is intended to allow for easiy parsing of the data (e.g., using a spreadsheet). It also explains the SOCRATES search queries and provides examples of their use.

CSV Data Format (RFC 4180):

The file begins with a list of fields used in the data and is then followed by the individual entries for each conjunction. Additional information can be found in the Notes below the table, which are also shown at the bottom of each table of SOCRATES search results.

Field	Description
NORAD_CAT_ID_1	NORAD Catalog Number for the first object. Note that this is the first of the two objects involved in the conjunction and not what might be considered the primary object.
OBJECT_NAME_1	Satellite name for the first object, extracted from the CelesTrak SATCAT. The operational status of the object is appended to the name, in brackets.
DSE_1	Days since epoch for the first object. This is the time in days from the epoch of the GP data used in the calculation to the calculated time of closest approach (TCA) and is an indication of how accurate the data might be at TCA.
NORAD_CAT_ID_2	NORAD Catalog Number for the second object. Note that this is the second of the two objects involved in the conjunction and not what might be considered the secondary object.
OBJECT_NAME_2	Satellite name for the second object, extracted from the CelesTrak SATCAT. The operational status of the object is appended to the name, in brackets.
DSE_2	Days since epoch for the second object. This is the time in days from the epoch of the GP data used in the calculation to the calculated time of closest approach (TCA) and is an indication of how accurate the data might be at TCA.
TCA	Time of closest approach.
TCA_RANGE	The distance or range between the two objects at TCA. Often referred to as the minimum range.
TCA_RELATIVE_SPEED	The magnitude of the relative velocity at TCA. This value provides an indication of the risk (specific kinetic energy) for the two objects if they collided.
MAX_PROB	Maximum probability (see Notes).
DILUTION	Dilution threshold (see Notes).

Notes

Data Fields:

Data: The GP Data button links to a page which provides the GP data used to generate the associated prediction.
NORAD Catalog Number: NORAD Catalog Numbers of the two conjuncting objects.
Name: SATCAT names of the two conjuncting objects. Operational status of each object is shown in brackets, using the standard CelesTrak SATCAT codes.
Days Since Epoch: The number of days from the epoch of the NORAD GP or SupGP (green) element set used to produce the prediction until the time of closest approach for the conjunction.
TCA (UTC): Time of closest approach.
Min Range (km): The distance between the two conjuncting objects at the time of closest approach.
Relative Speed (km/sec): Relative speed of the two conjuncting objects at the time of closest approach.
Max Probability: Given fixed spherical object radii and relative distance at the time of closest approach (TCA), the projected covariance ellipse is sized and oriented to produce the maximum probability. For these reports the ratio of major-to-minor axes of the projected covariance ellipse is set using radial, in-track, and cross-track values of 100 m, 300 m, 100 m, respectively. If the combined object radius is greater than the relative distance, the maximum probability will be one; such occurrences are not addressed here. For more details on the maximum probability method, see Dr. Sal Alfano's paper titled "Relating Position Uncertainty to Maximum Conjunction Probability".
Dilution Threshold (km): The standard deviation that produces the maximum probability defines the threshold of dilution. A smaller or larger standard deviation will produce a smaller probability. In the case of computing true probability with a smaller standard deviation, the data is of sufficient quality to associate low probability with low risk. For a larger standard deviation, this is not the case and the resulting true probability calculation becomes "diluted." If operating in this dilution region, the recommendation is to obtain better data and reassess the encounter. If time or resources do not permit, then the maximum probability should be used in place of the true probability.
SGP4 Propagation Errors: A list of objects which were not screened because their GP data shows they have already decayed (but haven't yet been reflected in the SATCAT) or will decay prior to the end of the computation interval.

All SOCRATES queries take the form:

https://celestrak.org/SOCRATES-Plus/table-socrates.php?{QUERY}=VALUE1&ORDER=VALUE2&MAX=VALUE3

where {QUERY} is:

NAME: Satellite Name. Allows searching for satellites by parts of their name. May use 0, 1, or 2 names, separated by a comma.
CATNR: Catalog Number. Allows return of data for satellites by catalog number. May use 0, 1, or 2 catalog numbers, separated by a comma.

where VALUE2 is:

MAXPROB: Maximum probability, sorted from largest to smallest.
MINRANGE: Minimum range, sorted from smallest to largest.
TCA: Time of closest approach, sorted from soonest to latest.
RELSPEED: Magnitude of relative velocity, sorted from fastest to slowest.
SSC: NORAD Catalog Number, sorted by smallest to largest for the first object and then for the second object.

All ties are sorted in order of increasing TCA.

and where VALUE3 is a positive integer less than the maximum allowed return of 1,000 conjunctions. If you want more results, you may wish to download the latest raw CSV results to search and filter using your spreadsheet software.

Examples:

The top 25 conjunctions sorted by minimum range (default search)
https://celestrak.org/SOCRATES-Plus/table-socrates.php?NAME=,&ORDER=MINRANGE&MAX=25
The first 25 conjunctions for the ISS (25544) sorted by minimum range
https://celestrak.org/SOCRATES-Plus/table-socrates.php?CATNR=25544,&ORDER=MINRANGE&MAX=25
The first 500 conjunctions between STARLINK and FLOCK satellites sorted by maximum probability
https://celestrak.org/SOCRATES-Plus/table-socrates.php?NAME=starlink,flock&ORDER=MAXPROB&MAX=500
The first 100 conjunctions sorted for ORBCOMM FM08 by NORAD Catalog Number
https://celestrak.org/SOCRATES-Plus/table-socrates.php?NAME=ORBCOMM FM08,&ORDER=SSC&MAX=100

Note that you can change the sort order for any set of search results by clicking on the appropriate re-sort order at the top of the search results table.

Legacy Text Data Format:

If you are using the .txt data files from the legacy SOCRATES system, the overall format is the same, without the header row. The ordering of the columns was modified, as well.

The CSV format uses:
```
NORAD_CAT_ID_1,OBJECT_NAME_1,DSE_1,NORAD_CAT_ID_2,OBJECT_NAME_2,DSE_2,TCA,TCA_RANGE,TCA_RELATIVE_SPEED,MAX_PROB,DILUTION
```
The TXT format used:
```
NORAD_CAT_ID_1,OBJECT_NAME_1,DSE_1,NORAD_CAT_ID_2,OBJECT_NAME_2,DSE_2,MAXPROB,DILUTION,TCA_RANGE,TCA_RELATIVE_SPEED,TIME_IN,TCA,TIME_OUT
```
The legacy data has extra columns for the TIME_IN (time entering the threshold) and TIME_OUT (time exiting the threshold).