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 the scientific merit and broader impacts of the proposed project. Potential users of the telescope should submit a proposal describing their desired observations or experiment, 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 website. Publicly-available information for currently scheduled proposals can be found on the web. This includes title, abstract, first author, time requested, and instrumental setup.

Please also see the FAQ for Arecibo Observatory Proposals. Information on the changes introduced at the September 1, 2016 Call for Proposals, and the rationale behind them, can be found here.

Table of Contents

    1. Cover Sheet
    2. Proposal Body
    1. Appeals
    1. Standard Proposals
    2. Director's Discretionary Time Proposals
    1. In Absentia Onserving
    2. Remote Observing


The deadlines for normal proposal submission are the first Thursdays of March and September, standard proposals (with the exception of Short Proposals) may be submitted between the Call for Proposals (normally issued around a month before the deadline) and the deadline. Not all observing modes will necessarily be available at every deadline: proposers should refer to the Call for Proposals for the deadline in question to see if any modes or instruments are not available or not accepting proposals.

The Observatory reserves the right to invite other proposals for specific purposes at any time.


A proposal is composed of two parts: the cover sheet, and the proposal body (containing the scientific and technical justification).

The cover sheet portion of the proposal is 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 (for astronomical observations) a list of the object(s) to be observed. After filling in all the specified information, you may preview a PDF version of the form to check for completeness and accuracy.

The cover sheet is LaTeX based, although we hope to move away from this in the near future. 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 PDF viewer should let you save a copy of the cover sheet. If you have difficulty with the web-based form, contact Edgard Rivera-Valentin at eriverav (at) for assistance.

Please note that the limitations of the LaTeX processing system mean that accented characters cannot be used in the outreach abstract. We are working to replace the current system with a more flexible system that will allow such characters to be used.

The proposal body must be submitted separately as a a PDF file. This should be uploaded using the same web-based form as the coversheet. The total size should not exceed 10MB. Please do not send gzipped files. If you have problems uploading your file, please contact us.


3.1 Cover Sheet

The web cover sheet must be filled out completely and submitted successfully prior to uploading the rest of the proposal. The cover sheet includes:

3.1.1 Observing Time

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 single semester, you can also ask for time during 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 is planned to continue beyond one year, you must estimate the remaining time required to complete 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 slot. The distribution of days, constraints due to object/phenomenon 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 length of the minimum usable block of time for individual observing sessions that is acceptable to you.

3.1.2 Auxiliary Equipment

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.

3.2 Proposal body

This should be a single PDF file, uploaded via the web form. The proposal body will normally be three pages long, except for large projects (6 pages) and short/urgent proposals (1 page), not including references and the source list. It should be formatted for US Letter (8.5" x 11") paper, with 1" margins and font size no smaller than 11pt. The proposal body should contain the following sections:

NOTE: There is no need to repeat the author list and abstract in the proposal body as these are on the cover that is sent to the referees.


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 Arecibo 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, which is used as input for the time allocation and scheduling process. ASAC contains both internal (Arecibo staff) and external members.

After the referees' reports are received, the ASAC meets and assigns a letter grade, A, B, C, or D to each proposal. A and B graded proposals are considered "approved projects". Proposers are sent the referee reports and the letter grade, as well as any specific comments or requests for clarification from the ASAC.

The Observatory Director, in consultation with the Deputy Directors for the scientific fields, has final discretion in scheduling matters.

Approved projects will be assigned a staff scientist to serve as their contact "friend of the telescope" when they receive their notification from ASAC. If required, observers are encouraged to contact this person well before the start date of the observations to discuss observing details. PIs will receive automated notifications when their proposal is scheduled.

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 and grades, 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 necessity 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:

Please note that PIs will only receive detailed information about their own projects, although cover sheets for all approved and scheduled projects are normally available via the Observatory web site. If there are specific reasons why cover sheets cannot be made public (e.g. confirmation follow-up of unannounced discoveries likely to attract widespread attention), the PI should discuss this with the Observatory at the earliest possible moment.

4.1 Appeals

Requests for ASAC to reconsider the grade awarded should be addressed to the ASAC chair. The final decision on scheduling remains with the Observatory Director in consultation with the relevant scientific Deputy Director.


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

5.1 Standard Proposals:

These proposals are handled by ASAC. With the exception of Short Proposals, they should be submitted for one of the standard telescope deadlines.

5.1.1 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).

The proposers should submit the cover sheet and a brief justification (one page or less). In the absence of conflict, and at the Observatory's discretion, the observation will be scheduled at the earliest convenient time.

5.1.2 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 proposal body of a regular proposal may be up to 3 pages long.

5.1.3 Large Proposals

These are for projects that request more than 300 hours of observing time (including proposals expected to request more than 300 hours spread over multiple years). The narrative of a large proposal may be up to 6 pages long.

Users intending to submit large proposals are strongly encouraged to contact relevant Arecibo staff in advance of submission to discuss their project.

5.1.4 Commensal (piggy-back) Proposals

A proposal may request observations to be scheduled simultaneously with a separate 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 other standard proposals. Scheduling will, of course, depend upon the availability of instrumentation.

Proposals for commensal observing are limited to either three or six pages depending on the number of commensal hours requested. These hours are not entered on the cover sheet as a time request, but should be mentioned (at least approximately) in the abstract. Proposals may have both a primary and a commensal component, in which case they should list only the hours of their primary request on the cover sheet.

ASAC will assess the full science delivered by an allocation of observing time, including the primary and any commensal proposals, in deciding on the grade for a project. However, the inclusion of a commensal partner will never cause a lower grade to be awarded to a primary project. Note that although commensal projects do not use telescope time as such, they are not "cost free", but can place a burden on Observatory staff and resources such as disk space. ASAC may therefore chose to reject commensal projects even if the primary is scheduled should they believe the effort required to carry out the observations has not been sufficiently justified.

Commensal projects will receive individual reviews from referees and comments from ASAC, but (unless rejected) will receive a joint ASAC grade with their primary project(s). When a commensal project has multiple primary partners, this could potentially mean the project will receive different grades for time requests with different partners.

5.1.5 Continuing Proposals

Standard Proposals that continue over a number of years may be granted "Continuing status" by ASAC on the basis that they have established a track record of receiving an A or B grade and are likely to continue to do so. Such proposals will only need to submit a cover sheet and a report to ASAC each year. The report can be up to three pages long (not including references). The cover sheet should specify the number of hours requested for the upcoming semester(s), as well as the total hours to finish the project.

In general, continuing status will be allocated only up to the number of hours requested to finish the project in the last fully refereed proposal. If it is necessary to substantially increase these, the proposers should inform the Observatory and submit a new full proposal rather than a report to ASAC.

Continuing status can be removed by ASAC if it is felt a full review is required for any reason, including (but not limited to) because the annual report is judged unsatisfactory, or because it has been a while since the project has been reviewed by the referees. If full review is requested, the time request may be granted for either the next semester or the next two semesters, at ASAC's discretion. In exceptional cases, ASAC may chose to recommend against scheduling a continuing proposal until it has undergone full review. Following a satisfactory review by the referees, ASAC may immediately reinstate continuing status without any need to establish a further track record.

5.2 Director's Discretionary Time Proposals:

This mechanism is for proposals that do not fit within the normal proposal procedure, either because of their urgency or other reasons. These proposals are handled by the Observatory Director, or on their behalf by the Deputy Director for the relevant science area, in consultation with the ASAC chair, telescope scheduler, and other relevant staff.

5.2.1 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 providing a scientific and/or technical justification. The Observatory Director or the Deputy Director for the relevant scientific area will respond to the request. At the Director's discretion, such proposals may be reviewed by appropriate external referees.

5.2.2 Special Scientific Proposals

Users interested in obtaining access to limited amounts of telescope time for "unconventional" observing programs are invited to propose for Director's Discretionary time. For example, an "unconventional" program may be exploratory observations to assess a speculative scientific idea. Special Proposals may, at the discretion of the Director, be sent to the referees or just reviewed by the ASAC. The Observatory Director or the Deputy Director for the relevant scientific area, informed by the recommendation of the ASAC, will decide whether to award time to the proposal. At the Observatory's discretion, proposals submitted in this classification may be reclassified into one of the scientific areas and handled by ASAC if it is felt that this is more appropriate.

5.2.3 Special EPO/Time-purchase Proposals

Users interested in running educational or other programs that purchase telescope time should contact the Observatory Director or the Deputy Director for the relevant scientific area in advance of submitting a proposal. A proposal consisting of only a cover sheet should be submitted once agreement has been reached, in order to enter the details into our scheduling system. These proposals may be submitted at any time, with the prior agreement of the Observatory.


We encourage the PI or a collaborator to be in residence during observations. However, we recognize that this may often not be possible and may sometimes be inefficient, as with routine monitoring programs. We therefore provide the option of requesting "In Absentia" or "Remote" observing where appropriate. Observers requesting remote observing should have experience using Arecibo; new observers are highly recommended to come to the Observatory for their first session unless they have a good remote mentor. In general, these are only appropriate for astronomy observations where the telescope is used passively and the setup can be entirely controlled by computer. For observations where more interactive control is needed of the telescope, users are encouraged to seek staff collaborators.

6.1 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 (at) The operator will initiate observing runs, communicate with investigators as necessary, and seek advice from Observatory scientific and technical staff. However, neither the operators nor other observatory staff are responsible for monitoring data quality. In Absentia observing is appropriate for observing programs that are simple and straight-forward to operate (particularly CIMA command file observing programs); complicated observing programs are not suitable for In Absentia observing.

6.2 Remote Observing

We define observing programs as Remote when the minute-to-minute conduct of the program is controlled from a remote site via electronic access. The telescope operator always retains final control and responsibility for the security of the telescope. Unless observers have recent experience running essentially identical observations for a different program, they must begin their program in residence at Arecibo to work out their program details. It is the responsibility of the PI to ensure that their 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 when circumstances 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 on the Remote Observing web page.

Remote observers must provide contact information in an email to remote (at) for the person who will actually carry out the observations at least three working days before the scheduled date of observation. Contact information must be valid for the time of the observation, e.g. for observations that will be carried out from home, an office phone number is not sufficient.


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 or the Deputy Director for the relevant scientific area. 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 from the end of observations on a particular object or field or the end of a particular experiment. The PI can request an extension of this period of up to one year by writing to the Observatory Director stating the reasons for which this is requested. This extension will be granted at the discretion of the Observatory Director in consultation with the relevant scientific Deputy Director. Scientific concepts and/or observing modes are not considered proprietary.

For Atmospheric observations, proprietary rights must be specifically requested. Data for which proprietary rights have not been requested (including World Days, etc.) will be uploaded to the Madrigal database after processing.

For Planetary Radar observations, the CW spectrum will be made available for the observed object online at immediately following the observation. Higher order products such as ranges or delay-Doppler images can be withheld from this public archive upon request by the user.

Note that these exclusive rights refer to the scientific use of the data; the Observatory reserves the right to use data obtained with our facilities for RFI monitoring and other data-quality and technical purposes.

In keeping with the Observatory's responsibilities under the NASA Plan for Increasing Access to the Results of Scientific Research, an object may be deemed to be of interest to NASA or another U.S. government entity. Users carrying out observations of such an object will provide press-worthy data to the Observatory upon request, for release to the requesting government entity.


If two or more proposals request time to observe the same source, region of sky or object of study 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 Observatory Director will have the final authority in resolving conflicts.


Arecibo Observatory 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. M?ndez-Universidad Metropolitana, and the Universities Space Research Association."

Publications that use data from the Arecibo Planetary Radar ('S-Band') system should also include: "The Arecibo Planetary Radar Program is supported by the National Aeronautics and Space Administration under Grant No. NNX12AF24G issued through the Near Earth Object Observations program."


In addition to the facility equipment provided by Arecibo Observatory, 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. Advanced arrangements should be made with the Observatory Director 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 posted on the Observatory website and circulated by 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.


Observatory staff can be contacted at the following email addresses: