HST Science Search Help

This page describes how to use the HST Science Search form and describes the individual fields in that form.

Use the HST Science Search form to search the HST Archive Catalog by object name, position, observation date, proposal ID, wavelength, and data type. You can also mark data for retrieval using this interface.

This interface can retrieve data either to the archive staging area or directly to the destination you specify, so you can retrieve proprietary data (if you're priveleged to do so). To allow you to safely enter a destination username and password, we use the same security mechanism as many commercial sites.

Target Name

The name of the astronomical object you want to search for.

Resolver

The name resolver you want to use, if you want to get an object's coordinates. To resolve an object's name into its coordinates, enter the object name in the Object Name field, select either NED or SIMBAD for the resolver. When you click on the "Search" button, the script will get the coordinates before doing the search. A message will appear at the top of the results page showing you what coordinates were found for the object (or an error message if the name resolver didn't work for some reason).

You do not have to use a resolver. One of the choices in the resolver selection menu is Do not resolve. Use this when you would like to search the object name field.

We recommend that you use object-name resolution to find observations of fixed targets in the database. This is the most reliable way to look up observations, because the observer could have given the observation any name at all (for example, NGC1976 instead of M42, or PARALLEL-FIELD). However, if you do know the name of the object, you can select HST Target Name, in which case, the object name will not be resolved into coordinates, but will be used as a search qualification in the database.

The SIMBAD and NED object name resolvers can only resolve the names of fixed astronomical object; they cannot compute the positions of moving objects (planets, comets, etc.).

Right Ascension, Declination

The Right Ascension and Declination around which you want to search. A number of formats are accepted for the RA and Dec. Here are some examples:

    Decimal Degrees
       	185.63325 29.8959861111111
 
    Hours, minutes and Seconds
        12 22 31.98      29 53 45.55
        12h22m31.98s     29d53m45.55s
        12:22:31.98     +29:53:45.55
        12h22'31.98"     29d53'45.55"
        12h 22m 31.98s   29d 53m 45.55s
        12h 22' 31.98"   29d 53' 45.55"
        12h 22' 31.98"  -29d 53' 45.55"
        12h22'31".98    -29d53'45".55
        12h22m31s.98    -29o53m45s.55
        12h 22' 31".98  -29d 53' 45".55
     
    Hours/Degrees and Minutes (no seconds)
        12 22     29 53
        12h22m   +29d53m
        12h22m    29d53m
        12:22m    29:53m
        12h22'    29d53'
        12h 22m   29d 53m
        12h 22'   29d 53'
        12h 22'  -29d 53'

    The RA may be given in decimal degrees by 
    indicating a D or d after the degrees:
        12d 22m   29d 53m

Spacing is not important, as long as the value is unambiguous, and that you can delimit the hours/degrees, minutes, and (optional) seconds with letters, colons, spaces, or any character that's not a digit or a decimal point.

Note also that seconds of the form 31".98 or 31s.98 are accepted. This should make it easy to cut and paste values into these fields from electronic publications.

Radius

How far around the search position you would like to search, in arcminutes.

We compute the angular separation between each result dataset and the search center. (The results will be sorted on the angular separation by default.)

One result is that you can do fancy stuff like searching for all observations between 2 and 8 arcminutes from the center of a galaxy (just give 2 .. 8 for the radius).

Equinox

The equinox of the RA and Dec you have entered, either B1950 or J2000. This only affects the input coordinates; the output coordinates will always be J2000.

Start Time

The date of the observation. More specifically, the date and time, in GMT, on which the exposure was started. When specifying this date, you need to include a date and an optional time. The date can have any of the following formats (the month name can be spelled out or abbreviated to three letters; case is not significant):

      Jul 15 1994
      Jul 1994 15
      15 Jul 1994
      1994 Jul 15
      1994 15 Jul
      7/15/1994
      7-15-1994
      7.15.1994
    

If the day is omitted, the first day of the month is assumed. This means that a specification like "July 1994" will look for observations done on July 1 1994 00:00:00, not for observations done during July 1994. Note also that when entering a date with the month in numerical format, the American ordeing is used; i.e., the first number is the month.

If a time is omitted, then midnight (00:00:00) is assumed. Otherwise, you can specify a time in any of these formats:

      14:30
      14:30:20
      14:30:20:999
      14:30:20.9
      4am
      4 PM
      04:30:20 AM
    

To search for observations before a given date, use <, and for observations after a given date, use >. For example,

      > Jul 15 1994
      < Jul 15 1994
    

You can use the .. operator to search on a range of dates:

     Jul 1 1994 .. Aug 1 1995
   

This operator is inclusive on the first date and exclusive on the second.

Finally, you can search on a list of dates or date ranges. For example,

     Jul 1 1994 .. Jul 3 1994, 
     Dec 1 1995 .. Dec 6 1995
   

will search for observations done within either one of these date ranges.

Exposure Time

The commanded exposure time in seconds. You can use operators or ranges in this field; for example,

   < 100
   > 1000.0
   100 .. 1000

You can exclude a range of exposures using a comma:

  < 100, > 1000

Observer/PI Last Name

The last name of the principal investigator of the observation. We sometimes refer to this person as the "observer".

Proposal ID

The HST proposal number under which the observation was executed. This can be a numeric ID or a comma-separated list of numeric IDs. Any characters other than digits, commas, and spaces will cause an error message to be displayed. For example, instead of searching for GO-5916, simply specify 5916. Or to search for observations from either proposal 5410 or proposal 5916, specify 5410, 5916.

Target Description

A short description of the target, supplied by the observer. like target names, these may not always be reliable- one observer's CLUSTER OF GALAXIES may be another's ELLIPTICAL- but they are generally better than nothing (especially where solar system objects are concerned; planet, asteroid, and comet names are more likely to be spelled out in the target description than in the target name).

Every morning, we generate a list of all the target descriptions currently in use. This list is linked back to the HST Science Search page, so you can read through this list (or search it with your browser's find capability) and find datasets matching the description.

Dataset

The dataset name is the unique identifier for an HST observation. (For NICMOS and STIS, it can also represent an association of exposures.) This value can be wildcarded using a *. When you specify a dataset name, any instrument or wavelength specification will be ignored.

Apertures

Enter HST aperture(s); These examples50CCD, 50CORON, WF2-FIX, WF3-FIX are a subset of the complete list.

Filters

Enter HST filter name(s); for example F606W or F110W, F160W are a subset of the complete list.

Obset ID

The observation set within the program. This is usually the same as the visit number, though in a small number of cases it will be different. The obset ID is used as the fourth and fifth letters of a dataset name. You can enter a comma separated list here. If necessary, obset IDs will be padded with leading zeroes to two characters.

Instruments Here you select which instruments you want data from. We've divided the instruments into Imagers, Spectrographs, and Other, but instruments that are (or were) capable of producing either images or spectra will appear in both places. These buttons will help you select only images or spectra from a particular instrument.

Users with Javascript enabled in their browsers will see two little buttons here labelled ALL and NONE. These buttons will select or deselect all of the checkboxes in the section, so you don't have to go through hitting lots of checkboxes if you only want one instrument.

Imagers

In this section, select the kind of images you want to search for by selecting the instrument.

Spectrographs

In this section, select the kind of spectra you want to search for by selecting the instrument.

Notice that some instruments are capable of producing both images and spectra. In this case, the query will be properly built to search for the selected observation type for that instrument.

Other

Here you can select data from instruments that produce neither images nor spectra: the Fine Guidance Sensors (which produce astrometric, usually interferometric, data) and the High Speed Photometer (which produced photometric data). These are not checked by default.

Release Date

Select the release date for the data, in GMT. See the observation date for the entry format. HST data has a nominal proprietary period of one year (though in special cases, this may be shortened or extended). The Release Date field gives the end of the dataset's proprietary period.

Archive Date

This is the date on which a dataset was archived. If a dataset was archived more than once (for example, if it was reprocessed by the pipeline), then this will show the latest archive date.

About 75% of all science datasets are archived within 24 hours after the end of the observation (delays longer than this are usually due to problems in pipeline calibration, or if the data stream gets backed up. Delays like this are rare, however, and are more likely to apply to the newer instruments early in their careers.)

Observations - Science or Calibration

Choose Science (default) to get only science observations in the search results. Choose Calibration to get only calibration observations in the search results. At this time, you may not choose both options at the same time.

User Option

You may now search on any column in the mission database. Select the field you wish to search on and type in the qualification. You may find the valid range of values by clicking on the field name. NOTE that if you choose a field in BOTH the form and in the User Option field, then you may not get results or the result you expect.

Output Columns

You may choose the columns to be displayed in the output. A set of columns that are commonly requested has been chosen as a default.

The default set of columns is:

    Mark
	Dataset
	Target Name
	RA (J2000)
	Dec (J2000)
	Reference
	Start Time
	Exp Time
	Instrument
	Filters/Gratings
	Proposal ID
	Angular Separation (')
    

You remove output columns by highlighting the column to be removed and then clicking on the remove button to the right of the list of chosen output columns.

You may determine the order of column placement by highlighting a column and then clicking on the up or down buttons to the right of the list of chosen output columns.

You may add a column to the list of chosen columns. Select the desired column on the pull down menu beneath the list of chosen output columns. Then click on the add button. The column will be added to the bottom of the output column list.

Sort output by:

Choose how you want the output rows sorted. You can select up to three fields to sort on. the rows will be sorted in the order of the first sort field; if two rows have the same sort field, they will be sorted in order of the second sort field, and so on.

For each field, you can select that the rows be sorted in reverse order on that field by selecting the reverse checkbox. For example, you can sort the rows with the most recent observations first by selecting Observation Date for the first sort field and selecting the reverse checkbox next to it.

Maximum number of hits

Some queries will be capable of returning thousands of rows or more. Such large search results tend to use up memory on both the client and server sides, and aren't usually useful. By default, we limit the number of rows displayed to 100 rows, but you can increase (or decrease) this limit as needed.

Show SQL Query

Select this checkbox if you want to see the SQL query that the HST Search engine constructs from your query qualifications. The query will be shown at the end of the search results.

SQL (Standard Query Language, pronounced either "ess cue ell" or "sequel") is a language used by most relational database systems for retrieving information from database tables. The HST Search Page takes your search specifications and converts them to an SQL query to run on our database. Viewing the generated query is often useful for debugging, and may also be useful for SQL-literate users who want to see what logic was used in the query. (In fact, this may be useful for most people, since SQL is pretty easy to understand.)

Make Rows Distinct

Select this checkbox if you want to have a set of distinct rows displayed. This is useful if you would like to see a distinct list of objects with certain criteria e.g. all the objects with similar target description. To make this function useful, you should not select column names such as Dataset Name, Mark or Observation Date in as output columns as all output is considered when making rows distinct.

Display Options

You may choose one of three display options: HTML Form, a comma separated list, and Excel spreadsheet