Minutes of the first meeting of Cambridge Amateur Radio Astronomers

1. A meeting was held in Downing College on Saturday 31st July, 1999 of a newly-formed group of people interested in radio astronomy and, in particular, in the opportunity to revive the One-Mile Telescope (OMT) at the Mullard Radio Astronomy Observatory at Lord's Bridge. This instrument had not been used for research for some years and had fallen into disrepair, being used recently only by Peter Duffett-Smith (PJD-S) and Guy Pooley (GGP) for undergraduate projects. Those attending the meeting were Jenny Bailey, Tristram Cox, Matthew Arcus, Bernie Wright, Ken Appleby, GGP, and PJD-S. Apologies were received from David Brooke. The interests of the Mullard Observatory were represented by GGP, who was a member of the Astrophysics Group at the Cavendish Laboratory and who had responsibility for OMT operations. PJD-S was now on 5 years leave of absence from the Astrophysics Group.

2. The meeting began with a general discussion of the opportunities afforded by the OMT. This was a three-element interferometer with the elements arranged in an east-west line, each element being an 18-m polar-mounted steerable dish. The east and centre antennas were fixed and the west antenna was mounted on rails of about half a mile in length so that its spacing relative to the fixed antennas could be varied. The signals from the moveable antenna could be used with the signals from each of the fixed antennas to give two simultaneous interferometer spacings, with receivers for simultaneous reception in each of two bands centred on 408 and 1410 MHz. This was how things used to be! It was noted that only the centre antenna was currently functional, and only at 408 MHz. The instrument had been built to a high mechanical specification and was generally in good shape. However, the electrical systems were old and needed replacing. Spare parts were all but exhausted in some key systems, notably those measuring antenna pointing. New RF, IF and back-end receiver systems were needed.

3. The meeting considered what scientific programmes could be pursued using only the central antenna with new electronic systems. The following were thought to be of immediate interest:

• hydrogen-line spectrum;
• monitoring of bright sources;
• bright pulsar studies;
• Moon bounce at 430 and 1296 MHz in conjunction with an off-site 3.5-m dish belonging to Jenny Bailey;
• observations of the Sun and the Moon;
• lunar occultations;
• variable source studies;
• SETI.

The purposes of running any programme of refurbishment and study included:

• education, especially by giving school children access via internet links and personal visits;
• use by students for Part III projects;
• personal interest;
• real research, although it was recognised that there were limited opportunities here.

The meeting acknowledged that getting the OMT back to full working order as a synthesis mapping instrument would require a great deal of work and should be regarded only as a long-term goal.

4. The meeting then considered the improvements to the OMT which would be needed before beginning any scientific programmes. These included:

• fitting new encoders and pointing tell-back systems;
• interfacing with a computer for automatic control;
• fitting new receivers (front-ends, RF, IF and back ends) for a range of bands including 408, 430, 1296, 1407 MHz, and 5 GHz;
• revising the clock;
• installing remote access facilities.

Any "improvements" made to the instrument would be carefully controlled by a design authority which would need to consider (a) the appropriateness of each new item within the overall system design, (b) health and safety aspects, and (c) the need to balance modern techniques with the historical nature of the instrument (e.g., it might be thought appropriate to maintain, in large measure, the general appearance of the OMT control room, if not the antiquated functionality).

5. Sources of money and effort would need to be found. These might include a PUS grant from PPARC (money only), the Cavendish Laboratory (maintenance effort, loan of equipment), and private subscription (money, equipment, and effort). PJD-S agreed to draft a plan for consideration at the next meeting. Meanwhile, GGP would seek approval in principle from the Observatory. PJD-S