HARP Information

February 15, 2008

Current Status

HARP was commissioned and accepted by the JCMT in April 2007. However, the combined system HARP/ACSIS/OCS is still being actively worked on.

HARP has 16 receptors separated by 30 arcsec with a foot print of 2 arcmin. The spacing is not completely regular but are being measured and more accurate positions will be used in the future. Older data can after the implementation be re-reduced using the updated positions. The beamsize of each receptor is approximately ~14 arcsec.

Currently 14 of the 16 receptors are working - the unusable receptors are 4 (H03) and 15(H14). Non working mixers were replaced in September 2006 and March 2007. However, an additional mixer failed in September 2008 and we are currently out of spares. MRAO are repairing the spare mixers as well as making more spare mixers. Replacemnt of the two broken mixers are not expected before the fall of 2008.

The most common problem with HARP are bad baselines and intensity differencies between receptors leading to striped maps. This is worst for 13CO.

Tuning

The following map of the receptors shows how they appears on the sky for an position angle (PA) of zero. The software generally uses the notation H00 to H15. If you are using the H scheme please always include the H. Users more commonly number the receptors 1 to 16, and that numbering scheme is assumed if the H not is included.

Receptor Map

R13(H12)	R14(H13)	R15(H14)	R16(H15)
R12(H11)	R11(H10)	R10(H09)	R09(H08)
R05(H04)	R06(H05)	R07(H06)	R08(H07)
R04(H03)	R03(H02)	R02(H01)	R01(H00)

The tuning range is 325-375 GHz, and the median receiver temperature is about 170 K and system temperature is ~350K in band 2 weather. The following tables show the average receiver and system temperatures for the 16 receptors measured with the ACSIS total detectors in January 2008 at 345.8GHz.

Trx

181	162	N/A	192
193	192	186	115
118	109	176	137
N/A	190	163	201

Note that the actual footprint on the sky might be rotated with a multiple of 90 degrees from the footprint in the above table. This is due to restrictions on the motion of the K-mirror. Further, to save time the closest suitable K-mirror position is selected making the selection history dependent. The above footprint on the sky is not uncommon for a southern source.

Tsys

359	353	N/A	397
375	383	395	336
292	277	375	235
N/A	440	327	394

The above table shows the HARP array system temperatures as measured with the ACSIS total power detectors in January 2007 in band 2 weather at 345.8GHz.