[alma-config] Antenna Transporter constraints

[Stephane Guilloteau]

Dear Torben & Jaap

    As mentionned in the last teleconf, we are working on designing the ALMA
Compact
Array (ACA) configuration, as well as all other configurations. Because the
ACA will be
made of 6 to 8-m diameter antennas as densely packed as possible, there is a
strong
interaction between the transporter design/ station design/ and
configuration layout.

    ACA is only interesting if the antennas can be packed down to their
collision limit,
1.25 D or so. This means station pads will be separated by 8 to 10 m at
most. Yet, we
need for scientific application to have about 12 densely packed stations for
the ACA
configuration. . As an illustration, I have included an example of ACA
station layout with 12 7-m antennas and the 4 12-m antennas which will be
used for calibration purpose and Single-Dish observing. The accessibility
problem becomes critical, and may even impose to allow
the transporter to drive above a station to access the innermost antenna
pads.

       This is a serious concern, which may have tough consequences on the
station design,
as well as on the allowed weight for the ensemble ACA_Antenna+Transporter.

        It would be good if you could communicate us (F.Gueth J.Pety &
myself) all relevant
information on the current ideas about the transporter design & antenna
lift-off procedure.
We will then come back to you with more precise questions related to the ACA
layout.

        Best regards

            Stephane