Please note this is an archived page. For current proposal policies and guidelines please see here

Information About Observing Proposals and Policies

Use of the Arecibo Observatory (AO) is available on an equal, competitive basis to all scientists from throughout the world to pursue research in radio astronomy, radar astronomy, and atmospheric sciences. Observing time is granted on the basis of scientific merit and broader impacts of the proposed project. Potential users of the telescope should submit a proposal describing their desired observations, the scientific justification, and the broader impact for these. The procedures for submitting proposals, the mechanics of evaluation, and the life-cycle of these proposals, are outlined below.

Up-to-date information about the status of the telescope and available instrumentation is obtainable at the Arecibo Observatory web page ( The public information for currently scheduled proposals ( is available on the web. This includes title, abstract, first author, time requested, and instrument setup.




The deadlines for submission are March 1 and September 1, although proposals may be submitted at any time.


A proposal is composed of a cover sheet, and a scientific and technical justification. The cover sheet portion of the proposal is to be submitted via a web-based form and consists of a title, abstract, author contact information, time and instrument specifications for the proposed project, RFI considerations, and object(s) to be observed. The scientific and technical justification must be submitted separately as a postscript or a PDF file.

The web-based cover sheet can be accessed from or through the "Scientific Users" menu on the AO web page. After filling in all the specified information, you may preview a postscript or PDF version of the form to check for completeness and accuracy. This is a LaTeX based form. For those who are familiar with LaTeX, some math-mode code (math symbols, greek letters, etc.) will be accepted. Please do not include any formatting codes, as these will be ignored and may possibly cause processing errors. However, no knowledge of LaTeX is needed to use the form. If you are not familiar with LaTeX, any special symbols, such as dollar ($), number (#), percentage (%), must be preceded by a backslash (\). After submitting your cover sheet, a temporary ID code in the form of Principal Investigator's (PI) last name followed by a 12 digit number, will be assigned to your proposal. After submission, you can use the back buttons to choose preview again if you wish. Your postscript or PDF viewer should let you save a copy. If you have difficulty with the web-based form, contact Ellen Howell at ehowell (append for assistance.

Email your scientific and technical justification as a postscript or PDF file to proposal (append They can be sent as attachments, or (for postscript only) as the body of the email. Please do not send gzipped files. The subject of the email should be the temporary ID number assigned to your proposal without any additional text.


  1. The web cover sheet filled out completely and submitted successfully. It includes:
  2. Proposal body, as a single Postscript or PDF file emailed to proposal (append

NOTE: Some auxiliary equipment, such as the Photometers or the Ionosonde that are used for atmospheric research, require little user interaction. Other equipment is more complex and requires detailed set-up and operation for an experiment, for example the Fabry-Perot Interferometers or the Lidars. Users who want to utilize these instruments in their studies are strongly encouraged to contact the appropriate staff member to determine the proper configurations for observation. Because most such auxiliary equipment cannot be run unattended, an investigator must be on site to conduct these observations.


Following the submission of a proposal, the PI will be notified and provided with an identification number. If there are no obvious technical problems, the proposal will be sent to anonymous referees (not NAIC staff) with expertise in the proposed field. The referees' recommendations serve to guide the Arecibo Scheduling Advisory Committee (ASAC) in the relative ranking of all proposals. This is used as input for the time allocation and scheduling process.

After the referees' reports are received, the ASAC meets and assigns a letter grade, A, B, C, or D to each proposal. Proposers are sent the referee reports and the letter grade, as well as any specific comments or requests for clarification identified by the ASAC.

The NAIC Director has final discretion in scheduling matters.

The proposer will be notified when his or her proposal is scheduled, and assigned a staff scientist who will serve as the contact "friend of the telescope" for the project. Observers are encouraged to contact this person to discuss various details well before the start date of the observations.

It should be emphasized that because of the special requirements of the different research areas which use the telescope, and the semi-transit nature of the instrument, scheduling is a difficult task, and may require interaction between the telescope scheduler and the proposers to ensure the flexibility necessary to accommodate what are often conflicting demands. It is not always possible to schedule in a "linear" fashion strictly following priorities. Depending on circumstances, some proposals will take longer to be placed on the schedule.

The Observatory tries to accommodate the requests and needs of its users, taking into account such factors as the need to coordinate projects with other experiments at other observatories, and the relation of a project to a student's career planning.

The following is a summary of the information that proposers will receive via email:


On the cover sheet you are asked to assign your proposal to one of the following categories:

5.1 Regular Proposals

These are proposals that are generally completed within a one-year period, usually in one or a few observing sessions. Most proposals fall in this category. The narrative of a regular proposal can be up to 4 pages long.

5.2 Short Proposals

Observers having scientific objectives that can be accomplished in 3 hours or less of telescope time are invited to submit a short proposal, which may be submitted at any time (proposal deadline restrictions do not apply). These are currently restricted to radio-astronomical observations applying straightforward techniques, e.g., a determination of the HI spectrum of a galaxy, a small set of galactic HI or OH spectra, or the continuum measurement of source flux densities.

The proposers should submit the cover sheet and a brief justification (one page or less). In absence of conflict, and at NAIC's discretion, the observation will be scheduled at the earliest convenient time. If requested, we would be willing to provide support for observing. Such a service observing would be arranged by a staff scientist, i.e., the designated "friend of the telescope" for the project.

5.3 Urgent Proposals

We recognize that observing opportunities occur where the phenomena are short-lived, non-recurring, or of particular interest or urgency. In such cases, the proposers should submit the web-based cover sheet indicating that the submission is an urgent proposal, as well as provide a scientific and/or technical justification. The Observatory Director will respond to the request. If time permits, these proposals will be reviewed by appropriate anonymous outside reviewers.

5.4 Director's Discretionary Time

Users interested in obtaining access to limited amounts of telescope time for "unconventional" observing programs are invited to propose for Director's discretionary time. An "unconventional" program may be exploratory observations to assess a speculative scientific idea, or observations motivated by educational or outreach objectives, for example. Proposals for Director's discretionary time will be reviewed only by the ASAC. The Observatory Director, informed by the recommendation of the ASAC, will decide whether to award time to the proposal.

5.5 Commensal (piggy-back) Proposals

A proposal may request observations taken simultaneously with a scheduled primary observing project. Control of the telescope remains at all times with the primary experiment. These proposals will be handled in the same way as all others. Scheduling will, of course, depend upon the availability of instrumentation.

5.6 Large Proposals

These are for projects that ask for more than 300 hours of observing time. The narrative of a large proposal can be up to 7 pages long.


On the cover sheet you are asked to specify the requested observing time for the coming semester. If your project cannot be completed in that one semester, you can also ask for time for the following semester (in both cases the time request(s) must be justified in the body of the proposal). In the case of a project that will continue beyond one year, you must estimate the remaining time required to finish the project.

On the cover sheet you are also asked to specify the observing time requested in either LST, AST (Atlantic Standard Time = UT - 4 hours), or UT, and specify the number of observing days required for each time interval. The distribution of days, constraints due to object availability, or spacing of days can be described in a text window below the time intervals. For example, you may need 3 contiguous days in a one-month window, or 3 days, spaced 2 days apart for timing of a particular object's activity. Describe constraints as succinctly and completely as possible. The time requested and its distribution must be supported in the scientific justification part of the proposal. You may also note the minimum usable block of time for this project that is acceptable to you.


We encourage the PI or a collaborator to be in residence during observations. However, we recognize that this may not always be possible and may sometimes be inefficient as with routine monitoring programs. Therefore, there is the option of requesting In Absentia or Remote observing.

7.1 In Absentia Observing

In Absentia observing is intended to provide greater operational flexibility for scientists who either:

The observations will be carried out by the telescope operator according to the PIs instructions. Therefore, the PI should send, well in advance, detailed and clear procedural instructions and relevant information to the email address observe (append The operator will initiate observing runs, communicate with investigators as necessary, and seek advice from NAIC scientific and technical staff. However, the observatory operator or the staff are not responsible of monitoring data quality. In absentia observing is appropriate for observing programs that are simple and straight-forward to operate. Complicated observing programs are not suited to In Absentia observing.

7.2 Remote Observing

We define observing programs as remote when the minute-to-minute conduct of the program is dictated from a remote site via electronic access. The telescope operator always retains final control and responsibility for the security of the telescope. Unless the observers have recent experience running essentially identical observations for a different program, the observers must begin their program in residence at Arecibo to work out their program details. It is the responsibility of the PI that the observers understand how to perform the observing program and are aware of any changes in the user interface. Remote observers should provide backup plans for circumstances that interrupt remote telescope control (e.g. communications dropout) so as to insure a successful completion of the observing session. Remote observing simplifies travel logistics, but transfers more of the responsibility for successful observations from the Observatory to the PI.

More information on remote observing is available at the Remote Observing with the Arecibo Telescope (

Remote observers must provide contact information in an email to remote (append for the person who will actually do the observations at least three working days before the scheduled date of observation.


Observers are scheduled on the telescope with the understanding that they pursue the program described in their observing request. Observers wishing to deviate from their original program, exchange time with other observers, or make use of unassigned telescope time, should seek the consent of the Arecibo Observatory Director. In cases of emergency or last minute changes, contact the telescope operator.


Under normal circumstances, observers will have exclusive rights to their data for a period of 18 months. The PI can request an extension of this period by one year by writing a letter to the Observatory Director stating the reasons for which this is requested.


If two or more proposals request time to observe the same source or region of sky to achieve essentially the same scientific objectives, they are in conflict. In this case the ASAC has the discretion to recommend the resolution to this conflict. The NAIC Director will have the final authority in resolving conflicts.


NAIC kindly requests that papers making use of the Arecibo Observatory contain the following acknowledgment at the point in the text where the Observatory is first mentioned, preferably in the form of a footnote, or according to journal format: “The Arecibo Observatory is operated by SRI International under a cooperative agreement with the National Science Foundation (AST-1100968), and in alliance with Ana G. Méndez-Universidad Metropolitana, and the Universities Space Research Association.”.


In addition to the facility equipment provided by NAIC, observers may bring their own special purpose equipment. We encourage such initiatives by providing space, power, and access to the IF signal, etc. Telescope position and other monitoring data can be made available. Advance arrangement should be made with the Observatory Director in Arecibo, to guarantee a smooth installation.

If you are willing to permit unrestricted access to your equipment and provide full user documentation, it can be converted to 'facility' status; a significant benefit to all parties. The Observatory may then take over routine maintenance. Such arrangements are handled on a case-by-case basis. The technical specifications will be circulated via Newsletter, the WWW, and other means, so that the equipment becomes available to all who wish to use it. No co-authorship or other obligations are incurred, though professional courtesy warrants acknowledgment in publications resulting from use of such equipment.


In order to improve our facilities and services, we request observers who have completed an observing session to provide us with feedback about their experience. Please use the On-line Feedback Form ( to send us your comments.