There is no single officially published, modern value for the system temperature (Tsys) or SEFD of the 25 m Dwingeloo radio telescope that’s easy to point to. What follows is a reasonable engineering estimate, based on historical documentation and typical performance of similar 25 m class antennas.
Historical / technical context (from EVN-era documentation):
- Receiver temperature (T_rec) ~ 70 K
- Total system temperature (Tsys) ~ 200 K
That total Tsys includes:
- receiver noise
- sky background
- spillover and ground pickup
At L-band, an older 25 m dish like Dwingeloo typically has:
- Aperture efficiency eta_A ~ 0.55 to 0.65
- Typical DPFU (degrees per flux unit) ~ 0.1 K/Jy
Basic relation:
SEFD = Tsys / DPFU
Using the above values:
Tsys ~ 200 K
DPFU ~ 0.1 K/Jy
So:
SEFD ~ 200 K / (0.1 K/Jy)
SEFD ~ 2000 Jy
Order-of-magnitude summary:
- Tsys ~ 180 to 220 K
- SEFD ~ 1500 to 3000 Jy
This is entirely consistent with:
- a room-temperature (non-cryo) L-band receiver
- a classic 25 m dish from that era
- typical elevation and sky conditions
If you are doing sensitivity calculations (HI line work, interferometry, EME link budgets, etc.), 200 K Tsys and ~2000 Jy SEFD is a sensible starting assumption unless you have measured values from the current CAMRAS front end.