Currently, SSOS will search images from MegaCam and CFH12K on CFHT , SuprimeCam on Subaru, GMOS on Gemini, WFPC2, ACS, and WFC3 on HST, WFI, VIMOS, VIRCAM, SUSI/SUSI2, FORS1/2, EMMI, EFOSC, HAWKI,and NAOS/CONICA on various ESO telescopes, and WFI on AAT, and the SDSS. There are a total of 6.5 million images in the database. Other archives will be added in the future.
Again, if you have any doubts on the accuracy of either of ephemeris generator
or their abilities to parse the object name, you should
generate your ephemeris and submit it to
the Search by ephemeris option.
Time can be specified in any of the following formats:
YYYYMMDDHHMMSS YYYY-MM-DD HH:MM:SS YYYY/MM/DD HH:MM:SS YYYY-MM-DDTHH:MM:SS YYYY/MM/DDTHH:MM:SSThus the following examples are acceptable (and equivalent):
19680117053522 1968-01-17 05:35:22 1968/01/17 05:35:22 1968-01-17T05:35:22 1968/01/17T05:35:22Alternatively, you can use Julian Dates or Modified Julian Dates
2439872.7328935185 39872.2328935185For RA and Dec, use any of the following formats
HH:MM:SS.SS DD:MM:SS.SS HHhMMmSS.SSs DDdMMm.SS.SSs DDD.DDDDDDDDD DD.DDDDDDDDDbut not
HH MM SS.SS DD MM SS.SS(no spaces are allowed inside a coordinate) The following examples are acceptable.
12:34:56 12:34:56.7 12:34:56.78 12:34:56.789 12h34m56.789 188.7366209Note that if an RA is given sexigesimal format, it is assumed to be in hours, but if given in decimal format, it is assumed to be in degrees.
No checking is done on the ephemeris. It is up to the user
to ensure that the values are reasonable and that the observations
are in chronological order.
You can specify a range of dates to search. The dates can be specified in the same formats as in the "Search by ephemeris" section above (ie, . The date range will be rounded to the nearest integer day. If the date range is smaller, the search will take less time If you leave the boxes empty, they will default to earliest and latest available observations. The date range for the "Search by ephemeris" function are the first and last dates in the ephemeris
Obviously, real positional uncertainties are better represented by ellipses, and real positional uncertainties vary with time. Some of the ephemeris generators behind the search functions described above produce good error ellipses. Others do not. Having box-shaped positional uncertainties represents a compromise. Note also, while the coverage of the images is known in some cases to very high precision (for example the MegaCam images which have been processed with MegaPipe) others are known to fairly low accuracy (such most of the CFH12K archive).
Resolve to extension:
Resolve to X,Y:
The first step is to generate an ephemeris. This is done by a variety of methods as discussed above. Except for the "Search by ephemeris" function, the ephemeris is generated at 24 hour intervals.
The second step is to retrieve a the list of possible images, currently there are about 130 000 images. This list is clipped down the requested date range. It is also clipped by position: If the object never leaves the ecliptic, there is no point looking at an observation at Dec=73. Similarly, the RA range may be small either because the date range is short or because it is a slow moving, outer solar system object.
The third step is to match the ephemeris to the list of observations. For each observation the position is estimated at the midpoint of the exposure time. This is done by linearly interpolating the ephemeris. The linear interpolation is key to keeping the queries reasonably fast. Doing a full orbital prediction for each of the images is not feasible. This is sufficiently accurate for the majority of queries, where the object either moves slowly or in a fairly straight line. For faster moving, nearby objects, it may be necessary to supply a sample the ephemeris at higher resolution.
The search return page first returns some diagnostic information about the ephemeris generation and database querying. This can either be nearly instantaneous or take up to a minute. The cross-matching part typically takes less than 10 seconds unless further "Resolve to ..." flags are set. Each of the flags typically adds 1 second per found observation.
The links in the table are either direct links to the data (if the image is hosted at the CADC) or a link another query page which should return only the relevant image extensions (if the image is hosted at SMOKA). The direct links use CADC's getData utility.
In addition to the data links, there are two other buttons.
Clicking on the first button returns a "regions" file which
can be used to with the image display program
This will give you a line showing the (linearly) interpolated
orbit and circles indicating the positions of the object
on matching images.
The second button gives you a plot showing the orbit
of the object with as a line with red circles indicating
the location of matching images.