Last modified 10 years ago Last modified on 02/10/14 09:38:02

Infrequently Asked Questions

(and known bugs/problems)

You may also want to take a look at the Frequently Asked Questions list.



How do I file a problem report or suggestion for improvement?

We suggest you use our general feedback form, or email your reports/comments/suggestions to: You can also fill out our user survey so we can prioritize based on the needs of the user community.

You should also check that you are using the most recent version of VSO. The most recent link will always be available from the VSO homepage at

I have a digital data archive and I would like to make the data available through VSO. What do I have to do?

Please contact one of the VSO scientists (Rick Bogart, Joe Gurman, Frank Hill, Piet Martens) and let us know of your interest. Extension of data service providers is the highest priority for VSO. We have an adoptor's kit, and assistance available to help tie your archive into VSO.

The majority of the work from the provider is in attempting to describe your holdings in terms of the VSO Data Model, so that the VSO has accurate information about the type of information that your organization providers.

Are there limits to the number of query results returned? If so, what are they?

Yes. Each data provider may have limits to prevent their systems from returning exceptionally large results. Because of the way in which VSO breaks queries down into simpler queries for the individual data providers to process, it is difficult to say just how many records an individual data provider will return.

How do I know if the number of query results was truncated by the data server?

The results page lists two numbers -- the number of records returned, and the number of records found. If the two are not equal, it means that one the data providers has reached its internal limit, and not returned all of its records that matched the query. If the number of records found is not displayed, it suggests that the data provider had reached its limit, but did not determine how many additional records there were. [This should only occur if the cost in performing an exhaustive search would be prohibitive].

We are trying to find a good balance between obtaining the desired results, while preventing there from being an undue burden on individual data archives, and the mechanisms for handling this scenario may be changed in the future.

When I request data, do they have to go through the VSO? How long does it take to get the data?

No data go through VSO. VSO only handles the process of locating, and ordering the data. The actual data delivery is handled by the user and the individual data providers, although it is possible that some user interfaces may add additional value by automatically following URLs to download information. For more information about the transfer of data, see the API documentation on Transfer Negotiation. Additional information is available for the data providers, but is currently in the process of being updated.

When I submit a query, at the end of the list of results it says Session ID: followed by a long incomprehensible hexadecimal string. What does it mean?

You may be using an older version of VSO. Please make sure you are connecting to the most recent VSO Search Interface. We are experimenting with mechanisms for recording search parameters and/or results (at the option of the user), so that any particular useful query can automatically be regenerated if desired, or referred to in publication of results.

All queries seem to go through and require the (some organization) VSO site. What is virtual about the Virtual Solar Observatory?

There originally was a single prototype implementation at Stanford. That has since been replaced with a system that is distributed across Stanford, NASA, and NSO, not including the functionality at each of the individual data providers.

What is virtual about VSO is that there is no one master archive or database of all of the holdings. There is a point of entry that users or applications can interact with, to access data that is spread across multiple systems. This concept is commonly refered to as 'Data Virtualization'. Additionally, there is virtualization on another scale, as there is no one single server -- Although there is a reference system, at, its purpose is to provide a unified starting point to people new to the VSO, and is not involved with the actual processing of the VSO, which currently has multiplexors at SDAC, Stanford, and NSO.

The information in the server data registries does not always match what is actually searchable. Are the displayed data registries different from those used by the user interface?

Please send us details about what you have found that doesn't seem to be in agreement, or what query you used, that you had expected data to be returned for.

What do all the funny colors on the results pages mean?

For ease of navigating among large numbers of return results, every fifth entry from each data provider is highlighted in yellow, every tenth in green, and every hundredth in blue. No special significance attaches to these entries.


When I query data from the (Montana State University|Mauna Loa) archive, I get lists in which apparently identical data sets are reproduced from two to seven times. When I download these data sets, they are indeed identical.

Observations in the MSU Yohkoh SXT archive are catalogued individually but packaged together in orbit files. If several observations in the same file match the search criterion they will each return a record, but the records will all point to the same distribution file. Downloading any one will of course get you all the data in the orbit file.

Observations in the MLSO archive are stored in both JPEG and FITS formats. Although the observations occur in the listings twice, they point to different data products. It is possible that this may change in the future, depending on user feedback. #13

I don't see any data from the McMath? FTS Spectrometer, though it shows up in the NSO list of instruments.

The VSO has helped us to shed light on the fact that some metadata are not correct. In this particular case, most of the datasets listed from the Kitt Peak 512-Channel Magnetograph and from the Evans Spectroheliograph have end times earlier than the start times. Occasionally there are multiple entries that are apparently identical (e.g. KPVT Magnetograph 1993.04.10).

I don't see any data for the last day of my time range request from the GOLF instrument, even though I know it is there; it shows up if I extend the range of time by even one minute.

Please make sure you are using the most recent version of VSO. Early versions of VSO required the observation to be completely contained within the search range. The current implementation performs range matching by searching for non-vanishing intersection.

When I query the Stanford Heleioseismology Archive for ground-based data I sometimes see records whose start and end times are both outside my requested time interval.

Range matches (in this case, time range), is done by finding a non-vanishing intersection. If you would prefer a different type of range matching, please let us know, so we can prioritize new functionality.

The Stanford datasets are generally for sets of images spanning a long time interval, typically a day for ground-based instruments. Although the datasets have registered start and end times corresponding to the first and last images of the day, they are in fact searched by an index number corresponding to the day number, starting at local midnight. In order to assure that no relevant records are missed from sites whose observations can span two UT days, the Stanford server returns matches for both day numbers.

Internal Technical Notes

These technical notes have been developed as an internal resource to assist staff in maintaining the VSO.