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Hubble Space Telescope
ACS Analysis

ACS GO Visit Policy

GO Visits

Do you need to visit?

Almost everything you will need to do with your data can be done at your home institution. We are continually updating our web pages and documentation to provide you with the latest information. Our goal is to make analysis of your data as convenient for you as possible. If you have access to STScI's varied web pages, you can download your data, the latest calibration/reference files, and any documentation that you may need. In addition, all our documentation is available on paper or other media, which can be mailed by conventional means. If you have a specific question not addressed by the documentation, you can consult a data expert by sending email to If you subsequently need to speak with someone, a phone conference with a scientist can be arranged.

However, if your data do not conform to what you have learned from the documentation, or if you are undertaking particularly challenging analysis, you may want to consider visiting STScI. Below you will find instructions on how to arrange a successful visit.

Arranging Your Visit

When you want to come and visit STScI, be sure to contact at least 3 weeks prior to when you'd like to come.

To make things more efficient please include in your email to us the following information when requesting a visit:

* Your full name, affiliation, and address of home institution.

* Your desired arrival/departure dates/times.

* Your experience level with UNIX, IRAF, STSDAS, and HST data formats.

* Your GO proposal ID number and, if possible, the relevant dataset names.

* Whether or not you consent to your data being retrieved prior to your arrival (prior retrieval is highly encouraged to save time).

* The expected goals for your visit.

Full support may not be possible during major meetings (AAS, major in-house meetings). Full support is likely to be available immediately after such meetings if arranged sufficiently in advance. There may be some difficulty in arranging full support during holidays or travel periods such as the winter holidays and throughout the summer months, though every effort will be made to accommodate any request, given sufficient notice. Observers are always encouraged to notify us as much in advance as possible.

The Instrument Group will then assign an Instrument Scientist (IS) and a Data Analyst (DA) to assist you. The IS will contact you to ask you for some information concerning your program and goals for your visit. For example the IS will want to discuss your expectations - what do you hope to accomplish with this visit? What type of analysis do you wish to perform? Do you want/need to recalibrate your data? You should also do some preparation work before you arrive to familiarize yourself with your data (see next section), which will allow your visit to be more productive and efficient.

Questions the IS will ask you while arranging your visit


* Do you need to calibrate data taken in unsupported modes?

* Do you need to perform non-standard calibrations?

Science Goals

* Spectroscopy:

- Flux issues?

- Wavelength issues?

* Imaging:

- Photometry?

- Drizzling?

- Coronography issues?

Preparing For Your Visit

You need to think about what you want to accomplish while you are here, and determine, scientifically, what you want to do. If you come with a clear analysis plan, your DA will be able to show you how to implement that plan (rather than showing you everything that can be done with ACS data) in IRAF.

Even though you may have experience working with some HST data, ACS utilizes different file formats and processing techniques than other instruments. Before you visit, you should be sure to familiarize yourself with ACS data such that your visit progresses smoothly once you are here. Your IS/DA team will assume that you have done this and base their work plan accordingly.

Observers wishing to visit STScI for the purpose of working on ACS data:

* Should know the basics of optical/UV astronomy and ACS properties, as well as IRAF and UNIX.

* Should have read relevant documents ahead of time (IRAF Manual, UNIX Manual, STSDAS Manual, ACS Instrument Handbook, ACS Data Handbook), which are all available on the ACS web pages.

* Should have looked at the data prior to coming to STScI, and have specific goals for the data reduction and analysis. [Note: Past experience has shown that without this background preparation, very little 'quality' work is possible; most of the time is spent going over the basics of ACS data and the IRAF/STSDAS software.]

Traveling to STScI

Directions, Parking, Maps and JHU information can be found here.

Once you Arrive - What to Expect

If this is your first visit to STScI, you should check the Visitor Information page, where you can find maps and driving directions. When you arrive at the Institute, pull your car into the front driveway and go inside. The receptionist at the front desk will tell you where you can park and call your IS/DA to let them know you have arrived. You'll be handed a card for access to the parking lot and entering the building after hours, as well as a temporary ID badge. You should plan to arrive no later than 9am as your IS and DA will be available to support you only between the hours of 9am and 5pm during the days of your visit. (You may possibly arrange for alternate hours with them.)

Your assigned IS and DA will be expecting you and will have made themselves familiar with your program and your goals for this visit, based on information you previously gave them. You will need to bring only yourself and any notes you need; all documentation and software will be available for your use here at the Institute. Currently, the software being used at the Institute is NOAO Sun/IRAF Revision 2.12.2a (14 July 2004), STSDAS Version 3.5 (March 24, 2006), and DITHER Version 2.2 (31 January 2006).

Typically, the DA and IS will have a short discussion with you when you arrive to discuss the "battle plan", e.g.- analysis specifics, problems with the data or target acquisitions, etc., so that there is a clear understanding of how your time will be best spent while you are here. The DA and GO will then go through some calibration/analysis basics if needed; the IS will assist if necessary.

We request that you allow a minimum of two days and a maximum of five days for a visit. The DA will be able to assist you for a few hours (depending on your needs) during the first two days of your visit. Once you are comfortable with the data, you are expected to work on your own for the rest of your visit.

Upon completion of your goals, there will be a second meeting between you, the DA, and the IS to review the work and answer any remaining questions. The final part of the visit will involve filling out a short evaluation form (or having an exit interview if you prefer) to comment on the technical and human resources, and the support received.

We look forward to helping you reach your ACS data science goals.

-The ACS Group