Once per year, now in the northern autumn, the User Support Department of ESO launches a Paranal Service Mode User Satisfaction Survey campaign. While this survey is by default anonymous, respondents are afforded the opportunity to identify themselves and to provide their e-mail address (see below).

This report details the findings of the October/November 2025 survey campaign (hereafter referred to simply by October 2025), while previous such reports are found here.

We view these reports as an important way to

• close the loop with the ESO Community,
• gather information on issues that need to be addressed or reinforced,
• thank all respondents, and
• demonstrate clearly that such feedback is important to us! 

To this end, here we provide a summary of the responses received and trends in these responses over the last years, predominantly in the form of graphs. It should also be stressed that for those few cases where respondents did identify themselves and did make specific free-text comments we have contacted them by e-mail to address their particular comments.

Methodology and General Results

In October 2025, we asked Principal Investigators (PIs) of Service Mode runs scheduled for Paranal in Periods 115 and/or 116 (plus their then-active Phase 2 delegates) to complete the survey by a fixed deadline. We thus solicited a response from 435 PIs and their then-active Phase 2 delegates (349 individuals). Because of overlap this amounts to a total of 681 individuals, who were contacted via e-mail. A deadline was set for four weeks from the date of contact, until Nov 9th.

A total of 101 responses were received by the deadline (some 30 of which were not fully complete), representing an all-time low of 14.8% return rate.

Interactive Figure Features

The figures below are all interactive.  By this we mean:

• Puttling the cursor over the plot will display the data values on the screen.
• Clicking on the menu icon in the upper right (the three short parallel horizontal lines) will open a menu of print/download options.
• For those figures with legends to the right of the plot clicking on any entry in the legend will toggle display of the corresponding data within the graph.

As a start in detailing the results from the survey, in the figure below we show the number of responses we received per instrument. With a survey covering 15 instruments and an overall lower response rate, the average number of responses per instrument is quite low at 12.6, with X-SHOOTER users being more represented than the rest.

In the following two stacked histogram plots we present a general overview of user satisfaction (in percentage of responses) with two general items:

• the Phase 2 web documentation and
• the overall support provided by the User Support Department.

The plots, designed to show the trend in user satisfaction expressed in survey results since September 2015, clearly show the consistently high satisfaction with these services offered by the User Support Department.

p2 and Other Observation Preparation Tools

As in the past, we also asked about both the p2 tool and other, instrument-specific, observation preparation tools. For comparative purposes we include still the last P2PP results (through September 2018) for a direct side-by-side comparison of P2PP and p2. In general the satisfaction levels with p2 are good and have been stable over the past few years in terms of ease of use and functions provided. More than a quarter of the users have no opinion about the documentation for p2, which tends to indicate that the tool is intuituve enough that it requires little explanation, and that we have a base of returning users who do not need to learn how to use it anymore.

ESO has released a Phase 2 Application Programming Interface (API) that can be used to create, modify, or delete observation blocks (OBs), containers and an accompanying ReadMe file that define an observing run.  We asked respondents whether or not they had made use of this powerful facility.  The way they replied is shown below. In that plot we see that fractional use of the p2API is apparently unchanged from last year, but the reader should be alerted to the small number statistics here.

Since, with the exception of ObsPrep, the number of responses per observing preparation tool other than p2 is very limited (see the table below), any presentation of individual-tool responses on documentation, ease of use, or functionality would suffer from small number statistics. Thus, in the three figures below answers for all tools, except ObsPrep, are combined. The ObsPrep figures can be found further down the page. Some of these tools are aging and it has become sometimes difficult for users to install and use the software, which explains the shown level of dissatisfaction. However, please note that the sample shown here concerns a very small number of users as the table below reveals.

As the usage of the ObsPrep tool outweighs all the other tools combined (see above) we have separated out responses to our ObsPrep questions for display below. Starting with usage statistics in the upper left plot we see a suggestion that usage continues to increase, thanks to more and more instruments and observation modes being supported by the tool.

The overall satisfaction levels with ObsPrep remain at a high level, and we hope that we can increase the share of "very satisfied" users in that area.

Related to the above tools is, of course, the suite of Exposure Time Calculators. Thus, we asked survey participants the question, “How satisfied are you with the ETCs you have used?” The responses are shown below. Overall, the satisfaction level with the ETC has decreased a bit this year, although we must emphasize once more that the small number of responses received may impact negatively the appreciation of the tool.

Again we asked users to tell us how satisfied they are with the p2fc (finding chart generator) app within p2.  We asked how they liked the tool in terms of documentation and its usefulness (as compared to any other alternatives for producing finding charts), with the plots below displaying the results. The user satisfaction with the documentation remains high. The satisfaction with the service provided by p2fc remains at a high level, too.

And lastly we asked survey participants, "Which operating system(s) do you use for ESO tools (e.g. for proposal/observation preparation, data reduction), excluding any browser-based tools?" This information is obviously not used as an indicator of satisfaction with the tools or support, but rather is gathered to ensure that we have an understanding about the technical requirements that users may have for the tools. We strive to develop tools that are OS independent, but a few of the legacy observation preparation tools still require local installation. Furthermore, data reduction pipelines also need to be packaged and tested on specific OSs.

The breakdown of responses is shown in the figures below. Mac OS X retains its rank of number one OS among the surveyed users. The percentage of Windows users remains very small.

Within the Linux usage we see that Ubuntu is still the dominating distribution, its relative share being higher than ever.

Notes:

¹The total time allocated in Service Mode for Periods 115 and 116 was 10558.2 hours, while the corresponding number for Visitor Mode was 1595.9 hours. Thus, the October 2025 survey targeted PIs (and their then-active delegates) representing 86.9% of the total Paranal time allocation. This is a very similar fraction as for the previous year’s survey campaign (86.4%).