SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                 SCHEDULE 13G/A
                                (Rule 13d-102)

                 INFORMATION TO BE INCLUDED IN STATEMENTS FILED PURSUANT
              TO RULES 13d-1(b), (c) AND (d) AND AMENDMENTS THERETO FILED
                              PURSUANT TO 13d-2


                                DECEMBER 31, 2002

                      CHECK THE APPROPRIATE BOX TO DESIGNATE THE RULE
                        PURSUANT TO WHICH THIS SCHEDULE IS FILED:
                               [ x ] Rule 13d-1(b)
                               [   ] Rule 13d-1(c)
                               [   ] Rule 13d-1(d)

                                AMENDMENT NO. 6
                             
                                  ORBOTECH LTD.
-----------------------------------------------------------------------------
                             (Name of Issuer)



                                  COMMON STOCK
-----------------------------------------------------------------------------
                         (Title of Class of Securities)


                                   M75253100
-----------------------------------------------------------------------------
                               (CUSIP Number)



<PAGE>

CUSIP Number  M75253100
1) NAME OF REPORTING PERSON
   S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           J. & W. SELIGMAN & CO. INCORPORATED
           13-3043476

2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

                                                            (a) /   /
                                                            (b) / x /

3) SEC USE ONLY



4) CITIZENSHIP OR PLACE OF ORGANIZATION

           DELAWARE

                   (5) SOLE VOTING POWER                -0-
NUMBER OF SHARES
BENEFICIALLY OWNED (6) SHARED VOTING POWER         2,993,629*
BY EACH REPORTING
PERSON WITH        (7) SOLE DISPOSITIVE POWER           -0-

                   (8) SHARED DISPOSITIVE POWER    2,996,029*


9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

                                                   2,996,029*

10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES  /  /



11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

                                                          9.42%

12) TYPE OF REPORTING PERSON

        IA, CO


 J. & W. Seligman & Co. Incorporated (JWS), as investment adviser for
 Seligman Communications and Information Fund, Inc. (the Fund), may be deemed
 to beneficially own the shares reported herein by the Fund.
 Accordingly, the shares reported herein by JWS include those shares 
 separately reported herein by the Fund.

            --------------------------------------------------

<PAGE>

CUSIP Number  M75253100
1) NAME OF REPORTING PERSON
   S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           WILLIAM C. MORRIS

2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

                                                            (a) /   /
                                                            (b) / x /

3) SEC USE ONLY



4) CITIZENSHIP OR PLACE OF ORGANIZATION

           UNITED STATES

                   (5) SOLE VOTING POWER                -0-
NUMBER OF SHARES
BENEFICIALLY OWNED (6) SHARED VOTING POWER         2,993,629*
BY EACH REPORTING
PERSON WITH        (7) SOLE DISPOSITIVE POWER           -0-

                   (8) SHARED DISPOSITIVE POWER    2,996,029*


9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

       2,996,029*

10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES  /  /



11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)  

                                                                9.42%

12) TYPE OF REPORTING PERSON

        IN


*  William C. Morris, as the owner of a majority of the outstanding voting
 securities of J. & W. Seligman & Co. Incorporated (JWS), may be deemed to
 beneficially own the shares reported herein by JWS.  Accordingly, the shares
 reported herein by William C. Morris include those shares separately reported
 herein by JWS.

            --------------------------------------------------

<PAGE>

CUSIP Number  M75253100
1) NAME OF REPORTING PERSON
   S.S. OR I.R.S. IDENTIFICATION NO. OF ABOVE PERSON

           Seligman Communications & Information Fund, Inc.
           13-31544499

2) CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP

                                                            (a) /   /
                                                            (b) / x /

3) SEC USE ONLY



4) CITIZENSHIP OR PLACE OF ORGANIZATION

            Maryland


                   (5) SOLE VOTING POWER  -0-
NUMBER OF SHARES
BENEFICIALLY OWNED (6) SHARED VOTING POWER  2,640,000
BY EACH REPORTING
PERSON WITH        (7) SOLE DISPOSITIVE POWER  -0-

                   (8) SHARED DISPOSITIVE POWER 2,640,000


9) AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

       2,640,000

10) CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES  /  /



11) PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

     8.30%

12) TYPE OF REPORTING PERSON

        IC


            --------------------------------------------------

<PAGE>


Item 1(a) Name of Issuer:

          ORBOTECH LTD.

Item 1(b) Address of Issuer's Principal Executive Offices:

          4 MANNING ROAD
          BILERICA, MA  01821
                    
Item 2(a) Name of Person Filing:

          (1) J. & W. SELIGMAN & CO. INCORPORATED (JWS)
          (2) WILLIAM C. MORRIS (Mr. Morris)
          (3) SELIGMAN COMMUNICATIONS & INFORMATION FUND, INC. (the Fund)

Item 2(b) Address or Principal Business Office or, if none, Residence:

          100 PARK AVENUE
          NEW YORK, NEW YORK  10017

Item 2(c) Citizenship:

          (1) DELAWARE CORPORATION
          (2) UNITED STATES
          (3) MARYLAND

Item 2(d) Title of Class of Securities:

          COMMON STOCK

Item 2(e) CUSIP Number:

          M75253100

Item 3    If this statement is filed pursuant to Rules 13d-1(b), or 13d-2(b),
          check whether the person is filing as a:

          JWS is an investment adviser in accordance with 
          Rule 13d-1(b)(1)(ii)(E). Mr. Morris is a control person of JWS in
          accordance with Rule 13d-1(b)(1)(ii)(G). The Fund is an Investment
          Company registered under Section 8 of the Investment Company Act
          of 1940.
 

Item 4    Ownership.

    Incorporated by reference to Items (5)-(9) and (11) of the cover page
    pertaining to each reporting person.

    JWS, as investment adviser for the Fund, may be deemed to beneficially own
    the shares reported herein by the Fund.  Accordingly, the shares reported 
    herein by JWS include those shares separately reported herein by the Fund.

    Mr. Morris, as the owner of a majority of the outstanding voting securities
    of JWS, may be deemed to beneficially own the shares reported herein by JWS.
    Accordingly, the shares reported herein by Mr. Morris include those shares
    separately reported herein by JWS.


Item 5    Ownership of Five Percent or Less of a Class.

          NOT APPLICABLE

Item 6    Ownership of More than Five Percent on Behalf of Another Person.

          The shares reported herein by JWS include those shares separately
          reported herein by the Fund.

Item 7    Identification and Classification of the Subsidiary which acquired
          the security being reported on by the Parent Holding Company.

          NOT APPLICABLE

Item 8    Identification and Classification of Members of the Group.

          NOT APPLICABLE

<PAGE>

Item 9    Notice of Dissolution of Group.

          NOT APPLICABLE

Item 10   Certification

          By signing below I certify that, to the best of my
          knowledge and belief, the securities referred to above
          were acquired in the ordinary course of business and
          were not acquired for the purpose of and do not have
          the effect of changing or influencing the control of
          the issuer of such securities and were not acquired in
          connection with or as a participant in any transaction
          having such purpose or effect.



                             SIGNATURE

     After reasonable inquiry and to the best of my knowledge and belief,
 I certify that the information set forth in this statement is true,
complete and correct.

DATE: FEBRUARY 11, 2003


J. & W. SELIGMAN & CO. INCORPORATED

BY  /s/ THOMAS G. ROSE
   -------------------------------------
   Name: THOMAS G. ROSE
   Title: Senior Vice President, Finance



  /s/ Frank J. Nasta
----------------------------------------
Frank J. Nasta, as
Attorney-in-fact for William C. Morris



SELIGMAN COMMUNICATIONS & INFORMATION FUND, INC.
 
BY  /s/ THOMAS G. ROSE
   -------------------------------------
   Name: THOMAS G. ROSE
   Title: Vice President



<PAGE>

EXHIBIT

7.1      Agreement   of  Joint  Filing  between J. & W. Seligman & Co.
         Incorporated, William C. Morris and Seligman Communications &
         Information Fund, Inc. dated FEBRUARY 11, 2003 2002.

7.2      Power of Attorney for William C. Morris



                                   EXHIBIT 7.1

                            AGREEMENT OF JOINT FILING


J. & W. Seligman & Co. Incorporated, William C. Morris and Seligman
Communications & Information Fund, Inc. hereby agree that the Statement
on Schedule 13G to which this agreement is attached as an exhibit, as well as
all future amendments to such Statement, shall be filed jointly on behalf of
each of them.  This agreement is intended to satisfy the requirements of 
Rule 13d-1(f)(1)(iii) under the Securities Exchange Act of 1934, as amended.

Dated:  FEBRUARY 11, 2003


J. & W. SELIGMAN & CO. INCORPORATED

BY  /s/ THOMAS G. ROSE
   -------------------------------------
   Name: THOMAS G. ROSE
   Title: Senior Vice President, Finance



/s/ Frank J. Nasta
----------------------------------------
Frank J. Nasta, as
Attorney-in-fact for William C. Morris


Seligman Communications & Information Fund, Inc.

BY  /s/ THOMAS G. ROSE
   -------------------------------------
   Name: THOMAS G. ROSE
   Title: Vice President



<PAGE>

                 EXHIBIT 7.2

              POWER OF ATTORNEY FOR
                WILLIAM C. MORRIS


     KNOWN ALL MEN BY THESE PRESENTS,  that the undersigned hereby appoints 
Frank J. Nasta,  attorney-in-fact  and agent, with full power of substitution
and  resubstitution,  for in name and stead, to sign and file Forms 13D and 13G
promulgated  under Section 13 of the Securities  Exchange Act of 1934, as
amended,  or further Amendments  thereto,  and any and all applications or other
documents to be filed with the Securities and Exchange Commission  pertaining
thereto,  with full power and authority to do and perform all acts and things
requisite  and necessary to be done on the premises.  This  appointment  shall
be valid for the sole purpose stated above and shall be in effect and force,
unless sooner revoked by me in writing.


     Executed this 2nd day of February, 1998.


                                  /s/ William C. Morris
                                ------------------------------
                                     William C. Morris