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ISDC - Information System and Data Center FAQs (frequently-asked questions)

Category: Main -> ISDC

Question

Answer

How is data stored at the ISDC?

At GFZ Potsdam, CHAMP products are stored on a tape robot with a large disk cache. Storage management software automatically moves the products from disk to tape, back and forth, depending on numerous factors (workload of the tape robot, disk space utilization, file creation dates, file sizes, etc). The system is fast, but it is basically unpredictable how long it might take to fetch products from tape.
Therefore, ISDC does not permit users to interact directly with this system. Instead, users are asked to order products, then ISDC gets these files from either tape or disk (depending on where they are), and then files will be put into a dedicated user directory at GFZ's FTP server.

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Will there be anonymous ftp access to the CHAMP-ISDC server?

No. There will be no anonymous ftp access to CHAMP ISDC data. You need to register with the ISDC.

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How can I register with the ISDC?

Use the web-based registration form to do so. If you have a professional background in satellite geodesy, or somehow provide a brief, reasonable justification, usually your application will be approved and access will be granted.
For CHAMP-registrations you have to wait until you are authorized to request CHAMP-products.

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Can I use the CHAMP ISDC after receiving an email?

No. You need to wait for a second email with the final confirmation. You can explore all possibilities of the ISDC-Portal, but your Home-Directory has to be created and that lasts a bit of time.

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Why is my user directory empty when I first log into my user directory?

You haven't ordered products before. When you login into your user directory without having ordered products before, it will be empty.

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I understand that I can order CHAMP products over the web, can I also download files over the web?

No. Due to storage of older products on tape, all product requests must be put into a queue, and users have to wait for some time until theirs requests are processed. Data transfer is performed by ftp after submittal of your requests.

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How can I get Products from the ISDC?

The Information System and Data Center actually offers two different ways for requesting scientific data over the web: the Product Retrieval Mode and Product Batch Mode. A third mode, Express Delivery, is currently under development. (A fourth mode, direct delivery, is a push service for internal users only, because these users need to give ISDC write access to their machines).

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What kind of request type fits better to my needs ?

The Retrieval Mode of the CHAMP-ISDC website is most interactive and convenient, hence this mode is more suitable for new users. After submitting a product search, you can order files over the web. Unlike the Batch Mode (see below), there is no need to enter your user directory first and to upload a product request file. (After a while you still need to enter your user directory and fetch the files you ordered).
The Batch Mode provides an easy way to initiate more demanding requests, or to use the ISDC in a non-interactive, automated manner. If you periodically need to get products with large file sizes and/or many small product files, then choose this mode. This avoids web-related problems with long HTML tables and browser timeouts. This mode is also much simpler to use for any kind of automated operation: Periodically upload a product request list (a simple text file) into the directory on the ftp server and your requests will be processed. In any case, be careful not to exceed the quota (disk space limit) of your account, though.

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Where I can find my user directory and the requested products when the transfer is complete?

Your data will be stored in the subdirectory 'data' of your user directory on our FTP server data.gfz-potsdam.de. You can log into this server using your password provided to you during the First Time Registration. If you have problems entering the directory using a browser (e.g. Internet Explorer or Netscape), then try to use a FTP client.

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Why can't I request data when I just newly registered?

Updating your account information is a complex process. Our FTP-Servers must be synchronized with the new user data and directories have to be created. So requesting is not permitted until your FTP-account is reachable by the portal server.

Normally you can instantly request public data, when you select a mission in MyAccount, except CHAMP. Due to special restrictions mission-officers have to acknowledge your wish, by reading your statement text.

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Product Statistics
In ISDC archive are stored:
  • 21.04 TB of data
  • 34.11 Mio products
(update: 2018-06-20 04:30:01)