[evlatests] ACUs -- Old vs New

[Chris De Pree]

Very interesting, Rick - thanks for sharing. Are the four remaining 'old' ACU antennas scheduled for an update?
________________________________
From: evlatests <evlatests-bounces at listmgr.nrao.edu> on behalf of Rick Perley via evlatests <evlatests at listmgr.nrao.edu>
Sent: Thursday, May 29, 2025 6:27 PM
To: evlatests <evlatests at nrao.edu>
Subject: [evlatests] ACUs -- Old vs New

I continue to troll through the 'flux density' data, taken earlier this year.

The observations include many long slews between the sources, so I can judge how long it takes the antennas to move from one source to another, when the separation is large.

It is quickly seen there is a major difference between antennas:  ea04, 15, 18 and 20 are always on source before the others.  The difference can be large — up to 30 seconds (!!!) for really big azimuth changes (meaning, about 8.5 minutes for the fast antennas, vs 9 minutes for the slower ones, for a full turn in azimuth.)

What's special about those four antennas?  — They are all 'old' ACU antennas, and indeed are the only remaining 'old' ACU antennas.  (ea05 is 'old', but was out of the array).

Question:  Is this difference expected?

The good news:  For the 'new' antennas, the arrival times on source — even for the very longest slews — are identical — within 1 second even for slews longer than 8 minutes.

Rick




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