CN103353922A - OTF (optical transfer function) observation scanning method - Google Patents

Abstract

The invention relates to an OTF observation scanning method. The method comprises the steps as follows: one scanning area is divided into a plurality of rows; a plurality of interlaced rows are scanned each time; interlaced scanning is performed for a plurality of times; and the whole scanning area is scanned. One-time scanning can cover the whole area rapidly with the interlaced scanning method under the condition that parameters of the antenna scanning speeds, sampling intervals and time intervals of observation reference points are the same, so that influences of factors such as telescope system performance, weather changes and the like on the distribution of the whole area are reduced; and when a interlaced scanning result is subjected to remeshing processing, reference points of data of adjacent rows in one meshed area are observed at different time, different reference points are independent, and the sum of integration of reference points of different rows is effective integral time of the reference points, so that the integral time of the reference points can be determined according to 1/k during line by line scan, wherein the k is the scanning time of one scanning area.

Description

A kind of OTF observation scan method

 

Technical field

The present invention relates to the radio astronomical telescope field, be specifically related to a kind of OTF observation scan method.

Background technology

OTF(On The Fly) be a kind of observation procedure of radio telescope, antenna scans the zone of appointment with constant speed, and single lattice point is not followed the tracks of, and a plurality of source points can share reference point and black matrix calibration, save time; Because whole zone is scanned fast, system performance and weather over time will be smaller on the impact of observation.

For fear of causing not losing of information, OTF sweep parameter that some restrictions are arranged owing to sampling, can not be greater than " Nyquist interval " such as the spacing of adjacent two scan lines; Sampling interval, i.e. single integral time, it should obtain one group of needed shortest time of valid data greater than the receiver rear end; The required distance that the sampling interval internal antenna is inswept approaches with line space.

Carried out very intensive spatial sampling in the process of OTF observation, these sampled points not necessarily are spacedly distributed, and need further heavily gridding to process (regrid), to obtain the Grid data of common form.

Traditional scan mode is that a scanning area is divided into several rows, line by line scan (such as Fig. 1) since a direction, for a larger scanning area, want very fast scanning complete one time, will add fast scan speed, and add fast scan speed and mean the integral time that shortens each point; Each net point is short integral time after shortening the data regrid that means single sweep operation integral time of each point, and noise is large, needs multipass; Mean that antenna frequently turns around the sweep time that shortens every row, is unfavorable for improving observed efficiency; If sweep velocity is slow, the time of finishing single pass is longer, is unfavorable for reducing telescopic system performance and the impact of Changes in weather on observing.

In addition, to integral time of reference point be conditional, oversize meeting is lost time, and reduces observed efficiency, too shortly can increase noise; How long observe a reference point restricted by the factors such as receiver stability, angle of pitch variable quantity, the oversize meeting in interval causes the spectral line baseline uneven, and too weak point can be lost time; Near the data of the sampled point the value of certain net point is put thus during regrid in the certain limit are weighted with certain function according to the distance of this sampled point apart from net point, usually adopt the gaussian function; These of weighting to effective integral time of reference point with the effective integral time to the source equate for best.If the point in this scope shares a reference point, is exactly the integral time of single reference point to the effective integral of reference point so, will equal the effective integral time to the source integral time of single reference point.

How in the situation that does not add fast scan speed, fast whole zone is once covered, the factors such as system performance and Changes in weather that reduce are on the impact of whole areal distribution; How under the prerequisite that does not increase noise level, reduce the integral time to reference point, improve observed efficiency, become the technical issues that need to address.

Summary of the invention

The object of the invention is to overcome the defective of prior art, provide a kind of energy rapid Cover whole zone, to the little OTF observation scan method integral time of reference point, improved observed efficiency.

The technical scheme that realizes the object of the invention is: a kind of OTF observation scan method, a scanning area is divided into several rows, and scan a plurality of row separately at every turn, carry out staggered scanning repeatedly, finish the scanning of whole scanning area.

Described OTF observation scan method specifically comprises the following steps:

S1. calculate total line number in zone of scanning: n=sweep limit ÷ scanning line spacing

S2. set scanning times k, calculate each number of scanning lines x:x=n/k, the result of calculation number that rounds up;

S3. according to the reference point observation interval of setting and scanning used time of delegation, calculate how many row of scanning after, need reference point of observation;

S4. calculate the capable scanning pass m of i, i=1,2 ... n, m=i/x, the result of calculation number that rounds up;

When S5. calculating scanning i is capable, the line number y of actual scanning:

y=(i-1-x*(m-1))*k+m；

If S6. the line number y of actual scanning reaches the interval line number that needs the observation reference point, then observe reference point;

S7. since the capable continuation scanning of y;

S8. repeated execution of steps S4-S7 sets scanning pass k to reaching, and finishes.

The invention has the beneficial effects as follows :1. adopt the staggered scanning method, in the identical situation of the parameters such as antenna scanning speed, sampling interval, the observation reference point time interval, zone of single pass energy rapid Cover, heavily to process the spectral line of a rear position be that repeatedly the result is average in gridding, each time is separated by longer, the interior point of gridding scope is distributed in different time sections, so the factors such as telescopic system performance and Changes in weather that can reduce are on the impact of whole areal distribution; 2. interleaved result is when doing heavily gridding processing, the reference point that the data of adjacent several row are used in gridding zone is different time observation, the reference point of different rows is independently, sum integral time of the reference point of different rows is the effective integral time of reference point, so to integral time of reference point can be when lining by line scan 1/k, k is the scanning times of a scanning area.

Description of drawings

Fig. 1 is the synoptic diagram of lining by line scan in the prior art of the present invention;

Fig. 2 is the staggered scanning synoptic diagram of the embodiment of the invention 1;

Fig. 3 is process flow diagram of the present invention.

Embodiment

As shown in Figure 2, a kind of OTF observation staggered scanning method is divided into 3 scanning with the n of a scanning area is capable, and scan 1,4,7 the first time ... OK, scan 2,5,8 for the second time ... OK, scan for the third time 3,6,9 ... OK.

As shown in Figure 3, OTF observation staggered scanning method specifically may further comprise the steps:

S1. calculate total line number in zone of scanning: n=sweep limit ÷ scanning line spacing

S2. set scanning times k, calculate each number of scanning lines x:x=n/k, the result of calculation number that rounds up;

S3. according to the reference point observation interval of setting and scanning used time of delegation, calculate how many row of scanning after, need reference point of observation;

S4. calculate the capable scanning pass m of i, i=1,2 ... n, m=i/x, the result of calculation number that rounds up;

When S5. calculating scanning i is capable, the line number y of actual scanning:

y=(i-1-x*(m-1))*k+m；

If S6. the line number y of actual scanning reaches the interval line number that needs the observation reference point, then observe reference point;

S7. since the capable continuation scanning of y;

S8. repeated execution of steps S4-S7 sets scanning pass k to reaching, and finishes.

Scanning times k distinguishes the combined factors such as used T.T. and receiver stability, late time data processing requirements according to one of scanning and considers, generally divides 2-4 time.

Claims (3)

1. an OTF observation scan method is divided into several rows with a scanning area, it is characterized in that, scans a plurality of row separately at every turn, carries out staggered scanning repeatedly, finishes the scanning of whole scanning area.

2. OTF observation scan method according to claim 1 is characterized in that the method specifically comprises the following steps:

S1. calculate total line number in zone of scanning: n=sweep limit ÷ scanning line spacing

S2. set scanning times k, calculate each number of scanning lines x:x=n/k, the result of calculation number that rounds up;

S3. according to the reference point observation interval of setting and scanning used time of delegation, calculate how many row of scanning after, need reference point of observation;

S4. calculate the capable scanning pass m of i, i=1,2 ... n, m=i/x, the result of calculation number that rounds up;

When S5. calculating scanning i is capable, the line number y of actual scanning:

y=(i-1-x*(m-1))*k+m；

If S6. the line number y of actual scanning reaches the interval line number that needs the observation reference point, then observe reference point;

S7. since the capable continuation scanning of y;

S8. repeated execution of steps S4-S7 sets scanning pass k to reaching, and finishes.

3. OTF observation scan method according to claim 1 is characterized in that described value of retouching number of times k is 2-4.

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