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ChaSeR: Search and Retrieval from the Chandra Data Archive
Frequently Asked Questions
Questions
Answers
Q:
How can I tell how big the tar file is going to be?
A:
When you Browse data on the Retrieval screen, the browse window
will list the total size along the top. However, you should note
that the sizes are for the uncompressed products while transfer will
take place in compressed form; on average, the compression is about a
factor 2.
Q:
Why can't I cut-and-paste that horrible tar file name?
A:
Cutting and pasting from Java windows in Unix does not work very well.
That's why we write the file path to a log file, so you can
cut-and-paste from that (see next question). By the way, the
"horrible" name provides protection in case you are retrieving
proprietary data.
Q:
Where do I find the transfer log?
A:
The filename is "chaser.log" and it is located in the directory that you
specified on the Retrieval List screen.
Q:
How do I get the tar file(s) and what do I do with them?
A:
Issue the following commands:
ftp cda.harvard.edu
bin
cd <directory>
dir
mget *
bye
Use the full directory path given on the screen or in your logfile; do
not yet download tar files with names that contain "InProgress".
If the directory appears empty, the tar file is not yet ready; please
try again in a short while.
To use the tar file(s), on Unix systems:
tar tvf <file name> - to inspect the tar file's contents
tar xvf <file name> - to extract the files from the tar file
If there are multiple files because the request exceeded 2 GB:
cat <file name 1> ... <file name n> | tar tvf -
cat <file name 1> ... <file name n> | tar xvf -
Q:
I am running twm/tvwm/olwm; why are my ChaSeR screens mutilated?
A:
(Unix systems only)
This is not a ChaSeR problem, but something that affects many
Java applications.
The window managers in the twm family (twm, tvtwm, olwm, ...)
predate serious Java development and contain a number of bugs that had
not come to light until people started running Java applications like
ChaSeR. The Sun Java Developer site lists some 50 bugs but
states categorically that these window managers are not supported and
that these bugs will not be fixed. The only option is to switch to
another window manager, such as CDE, KDE, Gnome. To check which
window manager you are running, type:
ps -gax | grep wm
or:
ps -e | grep wm
If this returns twm or tvtwm, then you may expect
problems. Note that it affects not only the operation of
ChaSeR itself, but possibly also the the installation program;
it may hang during execution.
Q:
Are the exposure times that are displayed in the search results window
accurate?
A:
What is really listed as exposure time is the time "charged" to the
proposal. That is the actual exposure time ("good time"), except in a
few cases where the observation collected on purpose a large dead time
fraction.
Q:
I specified a large range in galactic coordinates, but the search
results bear no resemblance to that constraint. How come?
A:
This is a bug that will be corrected in the future. The search
constraint works reasonably well for fairly small rectangles that do
not cover one of the poles.
Q:
Where do I find data associated with Engineering Requests?
A:
ChaSeR cannot access data products associated with Engineering
Requests (ER). For access to ER data use
RetrievER.
Note that ERs do not contain any data that are of scientific interest
and users may safely ignore them.
This page is maintained by the Chandra Data Archive Operations
group
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