1mm VLBI Call for Proposals: Introduction

The National Radio Astronomy Observatory (NRAO) invites proposals for 1mm Very Long Baseline Interferometry (VLBI) using the phased output of the Atacama Large Millimeter/submillimeter Array (ALMA) and the Event Horizon Telescope (EHT) during ALMA Cycle 4.  Up to 5% of ALMA Cycle 4 observing time is available for VLBI, shared between 1mm and 3mm.  Note that the EHT without phased ALMA is not being offered as part of this Call.

The submission deadline for 1mm VLBI proposals is Thursday, 28 April 2016, at 23:59 UT.

An overview of phased ALMA and the EHT is provided below, and further technical information to support proposal preparation is available at the Proposal Preparation link above, and at the EHT web page for 1mm VLBI with ALMA and the EHT.

The same proposal (including scientific and technical justification) must be submitted in response to this Call for Proposals as that submitted to the ALMA Cycle 4 Call to request phased ALMA.  Proposal preparation is therefore through the ALMA Observing Tool (OT), which requires registration through the ALMA Science Portal beforehand.  The ALMA OT Quickstart Guide provides more information on how to use OT.  Proposers will then submit a PDF copy of their full ALMA Cycle 4 proposal through the 1mm VLBI Proposal Submission website by the above deadline.  Additional information on proposing to ALMA may be found in the ALMA Cycle 4 Proposer's Guide.

Proposers who need assistance with proposal preparation or have questions regarding the Call should contact NRAO staff via the NRAO Helpdesk.  To submit a helpdesk ticket with 1mm VLBI-related questions, login to the NRAO Helpdesk, select "Submit a Ticket", select the "General" option for Telescopes, and then select the "General Queries" department.  If you do not already have a user account on the NRAO Science Portal, you must create one before logging into the NRAO Helpdesk.

The ALMA Phasing Project

The ALMA Phasing Project (APP) has provided the hardware and software necessary to phase up the ALMA dishes to form a single station for VLBI.  It is an international collaboration led by MIT Haystack Observatory, including contributions from NRAO, MPIfR, ASIAA, NAOJ, University of Concepción, Harvard-Smithsonian CfA, and Onsala Space Observatory.  It has been funded by the ALMA North America Development Fund, the NSF Major Research Instrumentation Program, and associated cost sharing partners.  For ALMA Cycle 4 the phasing system is offered using Band 3 (λ~3mm) with the Global 3mm VLBI Array (see the semester 2016B Call for Proposals) and Band 6 (λ~1.3mm) with the EHT (this Call for Proposals).  In the future, other ALMA Bands (e.g., λ~0.85mm) may also be available.  The maximum bandwidth that can be output from the phasing system is 7.5GHz.  The fringe spacing on a baseline from ALMA to Mauna Kea (JCMT, SMA) is ~30μas at λ~1.3mm.  Further technical information about phased ALMA may be found in the ALMA Cycle 4 Technical Handbook.

The Event Horizon Telescope

The Event Horizon Telescope is a 1.3 mm VLBI array whose primary goal is to observe and image nearby supermassive black holes with sufficient angular resolution to resolve the hot material just outside the black hole event horizon.  The EHT network currently consists of telescopes in the US, Mexico, Chile, western Europe, and the South Pole that together provide a resolution of better than 30μas.  To provide the sensitivity required to observe sources at such fine detail, EHT partners have developed ultrawide-bandwidth instrumentation and correlation facilities capable of handling very high data rates.  For ALMA Cycle 4, the EHT is offering a limited amount of array time to enable new science programs that can make use of the EHT in conjunction with the APP.

Proposal Review Process

All proposals requesting both phased ALMA and EHT time will undergo review through the normal ALMA proposal review and time allocation process, as well as being reviewed by the EHT consortium.  The final 1mm VLBI observing schedule will comprise proposals of the highest scientific and technical merit that are also able to fit into the VLBI session given its scheduling constraints.

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