Science with the Virtual Observatory
2006 Summer School

Introduction to Nesssi

Authors: Roy Williams, Conrad Steenberg, Ray Plante, Joe Jacob, Matthew Graham,

These notes are companions to the presentation on Nesssi (PPT).

Exercise 1: Getting an NVO certificate

Go to the Nesssi page http://us-vo.org/nesssi
Click on the link labelled "Click here to try Nesssi"
Follow the link "if you do not have an NVO login". Fill in the form with your name and address and email, plus your desired username and password.
An email will arrive for you at that address; respond to this as directed.
You now have an NVO login. Go back to the first two steps, but now click on the link labelled "already have an NVO login", and fill in the username and password.
You will be redirected to the Nesssi web portal. Check that it is correct where it says "Your username is".
You can click on the services at the left and think about filling the forms. But we are having difficulties with this web side.

Exercise 2: Command-line invocation of the services.

Use your command-line tool to go to $NVOSS/nesssi, then run the setup as usual
```
% source ../bin/setup.csh
```
Copy the CA certificate for the NVO CA into your local environment:
```
% mkdir -p /etc/grid-security/certificates
% cp 85* /etc/grid-security/certificates
```
(note -- you may have to do this with sudo or as root)

Find your UID

% python
>>> import os
>>> print os.getuid()
501

Get a proxy from the NVO Certificate Store, using the username and password from Exercise 1, and drop the result into /tmp:
```
% java NesssiInit <username> <password> /tmp/x509up_u501
```
(note -- the last part of the filename is your UID)

Run the test service, called sleepyadd:

$ python
>>> import nesssi_client as nesssi
>>> nesssiServer=nesssi.client('https://envoy.cacr.caltech.edu:8443/clarens/',debug=0)
>>> sessionID = nesssiServer.sleepyadd.init()
>>> print "Your session ID is", sessionID
>>> nesssiServer.sleepyadd.run(sessionID, "-time 30 -n 52 -m 344")
(wait a few seconds for the prompt)
>>> msg = nesssiServer.sleepyadd.monitor(sessionID)
>>>print msg

(note -- you could also just run the code in sleepyadd/sleepyadd_client.py)

The monitor method shows you a URL that includes the sessionID. This points to the sandbox corresponding to your job. Copy/paste this URL into a browser, and look at the stdout file. Your job may be queued, you may need to return to this URL later when the job has run.

Exercise 3: Mosaic from DPOSS

Choose an RA and Dec in the northern hemisphere, and check to see if DPOSS has it. Build a URL like this (put in the POS as RA,Dec), and put the result in a browser:
```
http://envoy.cacr.caltech.edu:8080/dposssiap/siap?band=F&POS=49.1,60.1&SIZE=0.5
```
Make sure that there are image URLs returned -- otherwise your mosaic will not work. This is the same SIAP server that the mosaicker uses. You can try the other bands too (F, J, N)

Start up the secure batch job with the dpossmosaic service:

$ python
>>> import nesssi_client as nesssi
>>> nesssiServer=nesssi.client('https://envoy.cacr.caltech.edu:8443/clarens/',debug=0)
>>> args = "-ra 49.1 -dec 60.1 -rawidth 0.5 -decwidth 0.5 -filt f"
>>> session = dbsvr.dpossMosaic.mosaic(args)
>>> print "Your session ID is %s." % session
>>> msg = nesssiServer.dpossMosaic.monitor(session)
>>> print msg

When the job has run, there will be a file called "mosaic.fits" in the sandbox URL.

Exercise 4: Cutouts on the Teragrid

Read the instructions at http://www.us-vo.org/nesssi/cutout.html You will use Vizier and your favorite catalog to get a list of sky positions. Select your favorite wavebands from your favorite surveys, these include SDSS, 2MASS, Palomar-Quest, Galex, IRAS, FIRST, etc.
You can connect to the server at Caltech, as above, or you can use the Teragrid node at SDSC. The choices are
```
https://envoy.cacr.caltech.edu:8443/clarens/
https://dtf-test1.sdsc.teragrid.org:8443/clarens/
```