SPHEREx Data Explorer at IRSA: Searching
This section is an overview of how to do a Spectral Image search in
the SPHEREx Data Explorer at IRSA. (Other tabs at the top, such as the
Spectrophotometry Tool, are covered elsewhere.)
To execute a Spectral Image search, after entering your search
parameters, click on the blue "Submit" or "Search" button to actually
launch the search.
Contents of page/chapter:
+Searching using a HiPS image
+Spectral Image Position Search
+Multi-Object Search
+Timing Constraints
+Spectral Constraints
+No Constraints
+Tools
+Results
When you start a Spectral Image search, you have a HiPS image loaded that takes up
most of the browser area (see screenshot below). Overlaid on top of
the HiPS image, there are colorful polygons indicating the sky
coverage for the data currently available in the archive. This
representation is also called a multi-order
coverage map (MOC), and it's gotten a bit more confusing recently
because nearly the entire sky has been covered at least once (yellow
polygons) and the deep field coverage has been added (red polygons).
There is now an explicit legend in the top right of the default view;
you can toggle these layers off and on quickly from here.
Because of the way these MOCs are calculated and rendered, which is
on HEALPixels (the grey grid-like lines), the polygon 'cells' get
smaller and smaller near the edges of the coverage as it tries to
match the reality of the covered data. As you zoom in, the coverage
adapts and the edges of the coverage become smaller polygons to get
closer to the true coverage. The opacity of the rendered MOC changes
such that it becomes easier to see through it; once your entire field
of view is entirely in a region where there are data, the overlay
disappears to make it easier for you to place your target on top of
the background.
You can click, pan, and zoom in the image, and even define a region,
to select a search location; many of the same visualization tools are
available for this image as for any other image in this tool. (Interacting with images is covered in
another chapter, including how
to change the background HiPS image.) In order to get a more
complete view of the sky, you can collapse or expand the target
specification window in the lower left by clicking on the collapse
arrow in the upper right of the box.
⚠ Tips and
Troubleshooting
- The region that has been observed by SPHEREx may look strange in
this tool. SPHEREx is a polar orbiter, so the part of the sky that it
observes in any orbit "makes sense" (in terms of visualization) in
ecliptic coordinates. The default HiPS representation is in galactic
coordinates, and you can see the Galactic Plane in the DSS image used
for the background by default. You may be used to thinking about the
sky in equatorial coordinates (RA/Dec), which is yet a third
coordinate system. Moreover, all of these things are curved surfaces
being represented on your flat screen, so distortion is inevitable.
You can click and drag the HiPS image around, add a grid overlay with
coordinates in a variety of units, ask it to put north-up, ask it to
show you things in ecliptic coordinates explicitly, etc. There
is an example immediately below. See the
visualization chapter for more detailed information.
Searching the archive is straightforward -- the most common search is
a search by position on the sky for a single-target cone search.
- Spatial type
- Single object or multiple object -- searching a
list of positions is covered below.
- Query Type
-
You can specify exactly which kind of query type you would like --
that is, what kind of relationship your search results hae with your
entered position or shape, and the subsequent options change
accordingly, e.g., :
- Observation boundary contains point (default)
- The next option is simply the target coordinates.
- Observation boundary contains shape
- The next options become "Cone Shape" or "Polygon Shape" -- you
can enter just the center position and the cone radius, or the list of
vertices for a polygon. You can list between 3 and 15 vertices, where
each vertex is given by a J2000 ra/dec position pair, separated by
commas. Because you are requesting that the images meeting your
search criteria cover the entire region you are requesting, if you
make the shape large, it's likely that you will be left with no images
matching your criteria.
- Observation boundary is contained by shape
- The next options become "Cone Shape" or "Polygon Shape" -- you
can enter just the center position and the cone radius, or the list of
vertices for a polygon. You can list between 3 and 15 vertices, where
each vertex is given by a J2000 ra/dec position pair, separated by
commas. Because you are requesting that the images meeting your
search criteria are entirely contained by region you are requesting,
if you don't make the shape large enough, it's likely that you will be
left with no images matching your criteria.
- Observation boundary intersects shape
- The next options become "Cone Shape" or "Polygon Shape" -- you
can enter just the center position and the cone radius, or the list of
vertices for a polygon. You can list between 3 and 15 vertices, where
each vertex is given by a J2000 ra/dec position pair, separated by
commas.
- Central point (s_ra, s_dec) is contained by shape
- The next options become "Cone Shape" or "Polygon Shape" -- you
can enter just the center position and the cone radius, or the list of
vertices for a polygon. You can list between 3 and 15 vertices, where
each vertex is given by a J2000 ra/dec position pair, separated by
commas.
- Coordinates or Object Name.
- By default, it assumes you are searching on a single target. You
may enter a target name, and have either NED-then-Simbad or
Simbad-then-NED resolve the target name into coordinates. After it
resolves the name, it will tell you which resolver service it used,
and also what that service has for the object type:
Alternatively, you may enter coordinates directly. These coordinates
can be in decimal degrees or in hh:mm:ss dd:mm:ss format, or
Jhhmmss+ddmmss format. By default, it assumes you are working in J2000
coordinates; you can also specify galactic, ecliptic, or B1950
coordinates as follows:
- '46.53, -0.251 gal' means 46.53, -0.251 degrees in galactic
coordinates
- '12.7, +4.3 ecl' means 12.7, +4.3 degrees in ecliptic coordinates
- '19h17m 11d58m b1950' means 19h17m 11d58m in B1950 coordinates
- a source name like 'J140320.67+542028.6' is parsed as 14h03m20.67s
+54d20m28.6s.
- a source name like 'G102.0360+59.7715' is parsed as 102.0360
+59.7715 in galactic coordinates
Examples are given below the text entry box before you start typing in
the box.
As you are completing a valid coordinate entry, the tool echoes
back to you what it thinks you are entering. Look right below the box
in which you are typing the coordinates to see it dynamically change.
⚠ Tips and
Troubleshooting
- Pick your units from the drop-down first, and
then enter a number; if you enter a number and then select from the
drop-down, it will convert your number from the old units to the new
units. There are both upper and lower limits to your search radius;
the tool will tell you if you request something too big or too small.
- You do not have to have a position search to execute a search. You
can de-select the position tickbox and just search the entire archive
with other constraints as described here, or none at all. Note that
there are plenty of calibration files that are in the archive that
have no position attached to them, so searching with position
constraints automatically omits calibration files from the results.
- Title
- All of these searches will be managed in the Job Monitor. If you are submitting a
lot of jobs, keeping track of which job is which in list in the Job
Monitor can be difficult. Using the "Title" field near the bottom of
the search window, you can change the title by which the search will
be listed in the Job Monitor. You don't have to change it from the
default to be able to search, however. (Once you change it, though,
all subsequent searches you make will still have that same title.)
Click on the blue "Search" button to launch the search.
You can submit a list of targets to search. When you select this
choice, you can select a table that is already loaded in the tool, or
you can upload a list of targets. The chapter
on uploading covers file formats and syntax. In some cases, you
may need to help the tool understand the positions by specifying what
the position columns are -- if there are ra/dec columns, it will
likely guess those properly.
You can also help it understand what the position columns are, like
this:
After you have uploaded your list of targets, the rest of the search
form looks the same as for the single position
search, with all the same choices.
These search options are generally of the same sort as you get for the
ObsCore Timing
constraints. Activate these options by ticking the box to the left
of "Timing" on the search screen.
 |
This is the default option, where you want data
overlapping a specified date range, where you can specify UTC or MJD
times.
|
 |
This is the alternate option, where you want data
completed in the last x days (or other unit of time).
|
Click on the blue "Search" button to launch the search.
⚠ Tips and
Troubleshooting
- SPHEREx launched on 11 March 2025 and begain nominal operations on
1 May 2025. There are no data in the archive earlier than that.
- SPHEREx data are scheduled to be delivered to IRSA on an
approximately weekly basis. The most recent data in the archive could
be up to about a week old.
- You can launch a search that is unconstrained by position and
constrained solely by time to, e.g., obtain the most recently observed
data.
These search options are very similar to those you get for the ObsCore Spectral Coverage
constraints. Activate these options by ticking the box to the left
of "Spectral Coverage" on the search screen.
 |
This is the default option, where you can specify that you want
data from a particular SPHEREx band. If you tick the box asking for
the spectral coverage constraints to be applied, then at least one
band has to be selected. If you select just one band, then it will
serve you only images from that band.
|
 |
Here, you can request data containing a given wavelength.
|
 |
This is the alternate option, where you want data
overlapping a specified wavelength range.
|
Click on the blue "Search" button to launch the search.
⚠ Tips and
Troubleshooting
- You can launch a search that is unconstrained by position and
constrained solely by wavelength to, e.g., obtain all the data taken
at a given wavelength, or combine it with a time constraint to get all
the data taken within a certain time at a certain wavelength.
If you unselect all of the tickboxes and ask for an unconstrained
Spectral Image search, you will return all of the files in the
archive, including calibration files. These kinds of results will
become more and more overwhelming in time, as more files are added to
the SPHEREx archive.
The Spectrophotometry Tool was the first
tool to be integrated into the SPHEREx Data Explorer. Its
initial screen looks very similar to the spectral image search screen,
but it's different, so it is covered in its own
section.
The Mosaic Tool is the most recent
tool to be integrated into the SPHEREx Data Explorer. Its
initial screen looks very similar to the spectral image search screen,
but it's different, so it is covered in its own
section.
Results are described in detail in another
section.
The Visualization section has
much more information about interacting with images.
The Tables section has
much more information about interacting with tables in general.
The Catalogs section has much more
information about searching for IRSA catalogs. You can do
many other searches as well.
When you load a table, you get an x-y plot displayed as well. See the
Plots section for lots more information.